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Hystrichokolpoma eisenackii
Hystrichokolpoma eisenackii Williams and Downie, 1966
Tax. jr. synonym of Hystrichokolpoma cinctum Klumpp, 1953, according to Damassa, 1979.
Holotype: Williams and Downie, 1966, pl.17, fig.2, text-fig.46
Locus typicus: London Clay, Sheppey, Kent, England
Stratum typicum: Early Eocene
Translation Gocht, 1969: Geological Survey of Canada
Original diagnosis: Williams and Downie 1966, p. 176-177
Ellipsoidal central body with wall composed of two closely appressed layers-the smooth or granular endophragm and the thinner smooth periphragm. Endophragm continuing uninterrupted beneath processes formed from periphragm. Processes of two types, large ones with quadrate bases, cylindrical or tapering with open ends, and small slender processes, with ends open or closed. Antapical process much longer than others. Tabulation typical for genus. Number of slender processes on each cingular plate limited to two. Cingulum helicoidal. Anterior sulcal process considerably larger than other sulcals.
Dimensions: Range of dimensions observed: diameter of central body: 40-57 Ám; Length of broad processes: 20-30 Ám; Antapical process up to 47 Ám; Width of broad processes: 12-27 Ám; Length of slender processes: 13-20 Ám; Width of slender processes: 0.5-4 Ám.
Original description: Williams and Downie 1966, p. 178
H.eisenacki is characterised by the broad processes which taper distally to a restricted opening with entire or serrate margin. Frequently branching off from the large processes are small erect tubules with an open serrate distal margin; commonly there are three or four on each process. The equatorial processes are simple or branched, slender with slightly expanded distal openings. The four apical plates are rarely present; the archaeopyle has a broad sulcal notch. In the precingular series of plates, plate 6"" and its attendend process are considerably smaller than the other five plates and processes, being comparable in size to the anterior sulcal plate and process. In the postcingular series, plate 1""" and its process are the smallest of the series, the other four plates and processes approaching the precingular in size. The longest process, which tapers before expanding distally, marks the position of the single antapical plate. This process is usually closed and unbranched. There are six sulcal processes, one very large anterior processes and five very slender open or bifid or acuminate processes lying between plates 1""" and 5""". The single posterior intercalary process is little different in size and structure to the slender sulcal processes and occupies a position between 1""" and 1"""". The apical processes are usually simple, occasionally branched, tapering and open distally.
Gocht, 1969, p.53,54:
In Meckelfeld, H. eisenacki occurred in a number of samples from the Early Eocene and the Oligocene, but it was always represented only by isolated finds.
The authors separate this species from H. cinctum Klumpp, which it resembles, because of morphological differences: H. eisenacki, according to them, is differentiated from H. cinctum by an especially large sulcal process and by a smaller number of cingular processes. Also the pre- and postcingular processes have different shapes. Since then, Morgenroth, 1968? has emended the diagnosis of H. cinctum and determined the tabulation. The specimen which he illustrates could also belong to H. eisenacki. It should be pointed out, as a reservation, that the range of variation of neither species is known. Moreover, the author was
not able to check Klumpp"s original. Thus, the determination as eisenacki is definitely provisional. In any case, it seems certain that my finds are identical with those from the London Clay. The careful analyses by Williams and Downie and by Morgenroth are largely confirmed by the Meckelfeld material as well.
The apical calotte is present only in exceptional cases. As far as I could detect, it seems to have only four plates, whereas Morgenroth reports six apical plates. However, he interprets the anterior sulcal plate ("AS" in Williams and Downie), which does not detach, as 1", following the Gonyaulacysta pattern. Hence, according to his observations, the five apical plates still remain on the calotte.
The precingular plates bear inflated, differentiated appendages. These terminate distally in a broadly truncate, usually open tip, and somewhat farther down they give rise to two (or seldom more) narrow lateral appendages which branch again distally. The postcingular processes show a similar structure, but with the reverse orientation, i.e., the furcate lateral appendages face back toward the cingulum. The anterior sulcal process ("AS" in Williams and Downie, 1" in Morgenroth) resembles the six precingular appendages, but is slightly smaller. Of the five postcingulars, only four (2"""-5""") reach the antapical field; the smaller process 1""" stops halfway. In general, the pre- and postcingular processes are larger and more clearly differentiated dorsally than ventrally. The longitudinal furrow bears six narrow processes on the hypotheca; the lower three of these processes usually have somewhat enlarged bases. Sharply bounded sulcal fields (1""", p+p, ?7""" in Morgenroth, 1p in Williams and Downie) were not observed. The antapical process 1"""" is long and conical, but may have sinuations or short processes toward the distal end. The cingular fields bear narrow processes, individual or fused in pairs. Even within my not very abundant material, the variability of the pre- and postcingular processes is considerable. There are gradations from simple, saclike structures with only short sinuations to highly differentiated ones with long; furcate appendages. Also Williams and Downie stress that the number of cingular processes varies.
Occurrence: Early Eocene- Middle Oligocene.
Tax. jr. synonym of Hystrichokolpoma cinctum Klumpp, 1953, according to Damassa, 1979.
Holotype: Williams and Downie, 1966, pl.17, fig.2, text-fig.46
Locus typicus: London Clay, Sheppey, Kent, England
Stratum typicum: Early Eocene
Translation Gocht, 1969: Geological Survey of Canada
Original diagnosis: Williams and Downie 1966, p. 176-177
Ellipsoidal central body with wall composed of two closely appressed layers-the smooth or granular endophragm and the thinner smooth periphragm. Endophragm continuing uninterrupted beneath processes formed from periphragm. Processes of two types, large ones with quadrate bases, cylindrical or tapering with open ends, and small slender processes, with ends open or closed. Antapical process much longer than others. Tabulation typical for genus. Number of slender processes on each cingular plate limited to two. Cingulum helicoidal. Anterior sulcal process considerably larger than other sulcals.
Dimensions: Range of dimensions observed: diameter of central body: 40-57 Ám; Length of broad processes: 20-30 Ám; Antapical process up to 47 Ám; Width of broad processes: 12-27 Ám; Length of slender processes: 13-20 Ám; Width of slender processes: 0.5-4 Ám.
Original description: Williams and Downie 1966, p. 178
H.eisenacki is characterised by the broad processes which taper distally to a restricted opening with entire or serrate margin. Frequently branching off from the large processes are small erect tubules with an open serrate distal margin; commonly there are three or four on each process. The equatorial processes are simple or branched, slender with slightly expanded distal openings. The four apical plates are rarely present; the archaeopyle has a broad sulcal notch. In the precingular series of plates, plate 6"" and its attendend process are considerably smaller than the other five plates and processes, being comparable in size to the anterior sulcal plate and process. In the postcingular series, plate 1""" and its process are the smallest of the series, the other four plates and processes approaching the precingular in size. The longest process, which tapers before expanding distally, marks the position of the single antapical plate. This process is usually closed and unbranched. There are six sulcal processes, one very large anterior processes and five very slender open or bifid or acuminate processes lying between plates 1""" and 5""". The single posterior intercalary process is little different in size and structure to the slender sulcal processes and occupies a position between 1""" and 1"""". The apical processes are usually simple, occasionally branched, tapering and open distally.
Gocht, 1969, p.53,54:
In Meckelfeld, H. eisenacki occurred in a number of samples from the Early Eocene and the Oligocene, but it was always represented only by isolated finds.
The authors separate this species from H. cinctum Klumpp, which it resembles, because of morphological differences: H. eisenacki, according to them, is differentiated from H. cinctum by an especially large sulcal process and by a smaller number of cingular processes. Also the pre- and postcingular processes have different shapes. Since then, Morgenroth, 1968? has emended the diagnosis of H. cinctum and determined the tabulation. The specimen which he illustrates could also belong to H. eisenacki. It should be pointed out, as a reservation, that the range of variation of neither species is known. Moreover, the author was
not able to check Klumpp"s original. Thus, the determination as eisenacki is definitely provisional. In any case, it seems certain that my finds are identical with those from the London Clay. The careful analyses by Williams and Downie and by Morgenroth are largely confirmed by the Meckelfeld material as well.
The apical calotte is present only in exceptional cases. As far as I could detect, it seems to have only four plates, whereas Morgenroth reports six apical plates. However, he interprets the anterior sulcal plate ("AS" in Williams and Downie), which does not detach, as 1", following the Gonyaulacysta pattern. Hence, according to his observations, the five apical plates still remain on the calotte.
The precingular plates bear inflated, differentiated appendages. These terminate distally in a broadly truncate, usually open tip, and somewhat farther down they give rise to two (or seldom more) narrow lateral appendages which branch again distally. The postcingular processes show a similar structure, but with the reverse orientation, i.e., the furcate lateral appendages face back toward the cingulum. The anterior sulcal process ("AS" in Williams and Downie, 1" in Morgenroth) resembles the six precingular appendages, but is slightly smaller. Of the five postcingulars, only four (2"""-5""") reach the antapical field; the smaller process 1""" stops halfway. In general, the pre- and postcingular processes are larger and more clearly differentiated dorsally than ventrally. The longitudinal furrow bears six narrow processes on the hypotheca; the lower three of these processes usually have somewhat enlarged bases. Sharply bounded sulcal fields (1""", p+p, ?7""" in Morgenroth, 1p in Williams and Downie) were not observed. The antapical process 1"""" is long and conical, but may have sinuations or short processes toward the distal end. The cingular fields bear narrow processes, individual or fused in pairs. Even within my not very abundant material, the variability of the pre- and postcingular processes is considerable. There are gradations from simple, saclike structures with only short sinuations to highly differentiated ones with long; furcate appendages. Also Williams and Downie stress that the number of cingular processes varies.
Occurrence: Early Eocene- Middle Oligocene.