BRACHIOPODA, 887 
Shell smooth or radiately striated ; umbo of dorsal valve sub- 
central ; of ventral yalve sub-central, marginal, or prominent 
and cap-like, with an obscure triangular area traversed by a 
central line. 
The large muscular impressions of the attached valve are 
Fig. 193. Ventral valve. Fig, 194. Dorsal valve. 
Crania anomala, Muller. z Zetland, 
a, anterior adductors; a@', posterior adductors; c, posterior adjustors; c', cardinal 
muscle ; 7, 0, central and external adjustors. 
sometimes convex, in other species deeply excavated; those of 
the upper valve are usually convex, but in C. Parisiensis the 
anterior (central) pair are developed as prominent diverging 
apophyses. In C. tripartita, Mister, the nasal process divides 
the fixed valve into three cells.* 
C. Ignabergensis is equiyalye, and either quite free or very 
slightly attached. C. anomala is gregarious on rocks and stones 
in deep water, both in the North Sea and Mediterranean (40—90 
fathoms, living; 150 fathoms, dead; Forbes); the animal is 
orange-coloured, and its labial arms are thick, fringed with 
cirri, and disposed in a few horizontal gyrations (Fig. 195). 
Distribution, 5 species. Spitzbergen, Britain, Mediterranean, 
India, New South Wales. —150 fathoms. 
Fossil, 37 species. Lower Silurian—. Europe 
C. antiquissima, Hichw. (Pseudo-crania, M‘Coy), is free, and 
has the internal border of the valves smooth; the branchial 
impressions blend in front. Spondylobolus craniolaris, M‘Coy, 
is a small and obscure fossil, from the Lower Silurian shale of 
Builth. The upper valve appears to have been like Crania, the 
lower to haye had a small grooved beak, with blunt, tooth-like © 
processes at the hinge-line. 
* M. Quenstedt has placed the Oolitic Cranias in Siphonaria! 
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