BRACHIOPODA. 
151 
by him as C. Schaurothi. Dall suggests* * * § that the species may represent a valid 
subdivision of the genus Crania ; but while the interior remains unknown, and 
the exterior is so similar to that of such species as C. setifera, C. setigera and C. 
spinifera , it would seem injudicious to assign it a distinct generic position. 
The generic term Pseudocrania, McCoy (Annals Nat. Hist., Second Series, 
vol. viii, p. 387), was proposed in 1851. The following diagnosis was given in 
British Palaeozoic Fossils, p. 187. 1855: 
“ Shell slightly inequivalve, free; both valves regular, depressed, subconical, 
unattached; dorsal valve with or without a small cardinal area; internally, 
margin broad, flat, smooth or minutely striated concentrically; anterior pair of 
muscular impressions much larger and more strongly marked than the posterior 
pair; pallial impressions numerous, linear, not interrupted along the middle. 
“ This palaeozoic genus differs from the true Cranise in the following points: 
(1) Crania is attached by the substance of the dorsal valve, and exhibits 
thereon an irregular scar; both valves are free and regular in Pseudocrania: 
(2) in Crania the posterior or marginal pair of adductor muscles are always 
la,rger and deeper than the medial or anterior pair; the reverse is remarkably 
the case in the presept genus, which also has a smooth or minutely striated 
margin, destitute of the strong granulation and punctures of most Craniae. 
The Crania antiquissima, as given by Yerneuil, may be taken as a type of the 
genus, as also the following species ” ( Pseudocrania divaricata, McCoy.) 
The first of these typical species, the 
Orbicula antiquissima , Eichwald,f = Crania 
antiquissima , Yerneuil,£ as represented by 
the latter author, shows a close similarity 
to Pholidops, Hall, in the character of its 
muscular scars. These are delineated as 
two central impressions abutting against a 
conspicuous posterior callosity, no evidence 
appearing of any posterior marginal scar corresponding to the posterior ad¬ 
ductors or divaricators of Crania. Mr. Davidson§ subsequently demonstrated 
a divaricata. 
After Davidson. 
Fig. 70. Interior of upper valve : a, adductors; l, ad¬ 
justors ;„m, mesenteric; r, divaricators; n.brachials. 
Fig. 71. Interior of lower valve. 
* Bulletin No. 8, U. S. National Museum, p. 19. 
f Silurian System in Esthland, p. 169. 1840. 
t G6ol. de la Russ, de l’Europe, etc., p. 289, pi. i, fig. 12. 1845. 
§ Silurian Brachiopoda, p. 79. 
