From Fensome et al., 2019:
Exochosphaeridium arnace Davey and Verdier, 1973, p.184–185, pl.1, figs.3,6. Holotype: Davey and Verdier, 1973, pl.1, figs.3, 6. Age: late Albian–early Cenomanian.

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Original diagnosis: Davey and Verdier, 1973, p.184
The central body is ovoidal in outline and often has a rounded apical protrusion. It appears to be surrounded laterally by a diffuse zone (3-5 µm in thickness) of a spongy, fibrous nature. Numerous relatively stiff, fibrous processes emanate from this zone, basically each possesses a broad base and tapers rapidly to terminate with a fine point or more rarely with a truncation. The sides of the processes are typically concave. The processes may be joined medially but are always joined proximally with neighbouring ones so as to give the appearance of a compact zone surrounding the central body. A distinctively branched apical process is present. A large, hoof-shaped precingular archaeopyle is always developed but other signs of tabulation are absent.
Dimensions: Holotype: central body length 45 µm, central body width 36 µm, process length 10-15 µm.