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Muiriella plioplax
Muiriella plioplax Churchill and Sarjeant, 1962; Emendation: Harland and Sarjeant, 1970, p.227–228
Holotype: Churchill and Sarjeant, 1962, pl.1, figs.20-21
Locus typicus: South Muir, SW Australia
Stratum typicum: Holocene
Original diagnosis: Churchill and Sarjeant, 1962, p.37
A species of Muiriella having a roughly spherical test,with epitheca and hypotheca each forming a hemisphere. Transverse furrow narrow, laevo-rotatory. Longitudinal furrow relatively broad, confined to the hypotheca; it apparently extends onto the antapex, but an antapical plate may be present. The crests bear spines, most commonly simple hut sometimes with bi- or trifurcate terminations; their length and spacing is variable.
Original description: Churchill and Sarjeant, 1962, p.37-38
Shell yellowish brown, not, or only very minutely, granular. Four apical plates: plate 1" is rectangular and corresponds in position to the anterior prolongation of the longitudinal furrow. Four anterior intercalary plates and at least nine pre-equatorial plates are present; plate 9" may be subdivided, as indicated by a broken line in Text fig. 3, but this was not confirmed. The transverse furrow forms a laevo-rotatory spiral such that its two ends differ in antero-posterior position by the furrow"s width: it is subdivided by ridges into at least five sections. The longitudinal furrow is separated from plate 1" by a small, square plate, here designated an anterior ventral plate; a second, similar plate may he present posterior to the first.
Seven post-equatorial plates are present, plate 1""" being reduced; three posterior intercalary platcs are present. The character of the antapex was not certainly determined.
The crests delimiting plates and the furrow boundaries have the form of low ridges, from which arise strong, short pro(esses. These processes typically have closed tips, but, in at least two instances on the holotype, they appear to take the form of tubes open distally. Dimensions. - Holotype: length 52.5 Ám, breadth 53.5 Ám, spines 3-5 Ám in length. Other specimens comparable (12 specimens).
Emended diagnosis: Harland and Sarjeant, 1970, p.227
A species of Muiriella having a roughly spherical test, with epitract and hypotract each forming a hemisphere. Cingulum of moderate breadth, laevo-rotatory: sulcus slightly broader, widening in its hypotractal portion, subdivided into three (or four) sections by transverse crests. Low crests define the tabulation; these give rise to short spines, commonly simple but sometimes with bi- or trifurcate terminations. The relative length and spacing of the crest spines is variable. The apex is typically lost in archaeopyle formation. The posterior surface is occupied by a group of small plates, here considered to fall into two distinct groups arranged about a single antapical plate.
Dimensions: Holotype: Length 52.5 Ám, breadth 53.5 Ám, spines 3-5 Ám in length. Other specimens comparable. (12 specimens.)
Emended description: Harland and Sarjeant, 1992, p.228
The condition, not only of the holotype but also of the other specimens contained in slide P26438, has markedly deteriorated in the period since the first study was made: the specimens appear to have contracted and folded, and it proved impossible to reconfirm all details originally observed. Fig. 8 is therefore based in part on the original sketches, in part on the new observations: the description is a revised restatement of the earlier description.
Shell yellowish brown, not (or only very minutely) granular. Apex lost in archaeopyle formation. Three anterior intercalary plates are present, situated on either side of the cingulum. Six or seven precingular plates are present, the boundary between plates 3" and 4" being obscured (if present) . Plate 1" is markedly reduced, plates 6" and 7" to a lesser degree, to accommodate the anterior intercalary plates.
The cingulum forms a laevo-rotatory spiral such that its two ends differ in antero-posterior position by the furrow"s width: it is subdivided into at least six cingular plates. The sulcus is divided into three or four plates by transverse crests.
Eight postcingular plates were recognized, with plate 8""" reduced to accommodate plate 2p. A cluster of small plates surrounds the antapex.
The crests delimiting plates and furrow boundaries have the form of low ridges from which arise strong, short processes. These processes typically have closed tips, but in at least two instances on the holotype, they appear to take the form of tubes open distally.
Holotype: Churchill and Sarjeant, 1962, pl.1, figs.20-21
Locus typicus: South Muir, SW Australia
Stratum typicum: Holocene
Original diagnosis: Churchill and Sarjeant, 1962, p.37
A species of Muiriella having a roughly spherical test,with epitheca and hypotheca each forming a hemisphere. Transverse furrow narrow, laevo-rotatory. Longitudinal furrow relatively broad, confined to the hypotheca; it apparently extends onto the antapex, but an antapical plate may be present. The crests bear spines, most commonly simple hut sometimes with bi- or trifurcate terminations; their length and spacing is variable.
Original description: Churchill and Sarjeant, 1962, p.37-38
Shell yellowish brown, not, or only very minutely, granular. Four apical plates: plate 1" is rectangular and corresponds in position to the anterior prolongation of the longitudinal furrow. Four anterior intercalary plates and at least nine pre-equatorial plates are present; plate 9" may be subdivided, as indicated by a broken line in Text fig. 3, but this was not confirmed. The transverse furrow forms a laevo-rotatory spiral such that its two ends differ in antero-posterior position by the furrow"s width: it is subdivided by ridges into at least five sections. The longitudinal furrow is separated from plate 1" by a small, square plate, here designated an anterior ventral plate; a second, similar plate may he present posterior to the first.
Seven post-equatorial plates are present, plate 1""" being reduced; three posterior intercalary platcs are present. The character of the antapex was not certainly determined.
The crests delimiting plates and the furrow boundaries have the form of low ridges, from which arise strong, short pro(esses. These processes typically have closed tips, but, in at least two instances on the holotype, they appear to take the form of tubes open distally. Dimensions. - Holotype: length 52.5 Ám, breadth 53.5 Ám, spines 3-5 Ám in length. Other specimens comparable (12 specimens).
Emended diagnosis: Harland and Sarjeant, 1970, p.227
A species of Muiriella having a roughly spherical test, with epitract and hypotract each forming a hemisphere. Cingulum of moderate breadth, laevo-rotatory: sulcus slightly broader, widening in its hypotractal portion, subdivided into three (or four) sections by transverse crests. Low crests define the tabulation; these give rise to short spines, commonly simple but sometimes with bi- or trifurcate terminations. The relative length and spacing of the crest spines is variable. The apex is typically lost in archaeopyle formation. The posterior surface is occupied by a group of small plates, here considered to fall into two distinct groups arranged about a single antapical plate.
Dimensions: Holotype: Length 52.5 Ám, breadth 53.5 Ám, spines 3-5 Ám in length. Other specimens comparable. (12 specimens.)
Emended description: Harland and Sarjeant, 1992, p.228
The condition, not only of the holotype but also of the other specimens contained in slide P26438, has markedly deteriorated in the period since the first study was made: the specimens appear to have contracted and folded, and it proved impossible to reconfirm all details originally observed. Fig. 8 is therefore based in part on the original sketches, in part on the new observations: the description is a revised restatement of the earlier description.
Shell yellowish brown, not (or only very minutely) granular. Apex lost in archaeopyle formation. Three anterior intercalary plates are present, situated on either side of the cingulum. Six or seven precingular plates are present, the boundary between plates 3" and 4" being obscured (if present) . Plate 1" is markedly reduced, plates 6" and 7" to a lesser degree, to accommodate the anterior intercalary plates.
The cingulum forms a laevo-rotatory spiral such that its two ends differ in antero-posterior position by the furrow"s width: it is subdivided into at least six cingular plates. The sulcus is divided into three or four plates by transverse crests.
Eight postcingular plates were recognized, with plate 8""" reduced to accommodate plate 2p. A cluster of small plates surrounds the antapex.
The crests delimiting plates and furrow boundaries have the form of low ridges from which arise strong, short processes. These processes typically have closed tips, but in at least two instances on the holotype, they appear to take the form of tubes open distally.