12 BRITISH CRETACEOUS BRACHIOPODA. 



terior ones are more or less circular, lying close, and partially surrounded by the inner 

 edge of the granulated margin ; these are separated from each other by an almost equally 

 wide and depressed space ; the anterior pair are situated towards the centre, united 

 together, and diverging in the form of a V, being more or less oval and depressed in the 

 centre ; between and above them is a small, produced, nose-shaped protuberance, the same 

 wide margin is likewise visible in the upper valve, which is deeper, with four corresponding 

 muscular impressions, disposed as in the attached valve, with this difference, that the 

 anterior pair are larger, and a hollow is seen between and above them, where the 

 projection in the lower valve exists. Structure punctuated ; vascular impressions well 

 defined. Dimensions variable; length 3, width 3, depth 1^ lines. 



Obs. This small Crania has received several names from different authors ; it seems, 

 however, to have been first noticed by Retzius under that name of Egnabergensis in 1781, 

 which denomination has been adopted by many Palaeontologists, although commonly 

 known also by that of C. striata ; C. ovalis of "Woodward is only an accidentally 

 elongated specimen of Retzius' species, and many specimens attributed to C. costata in 

 England, are only simple varieties of the form under examination with fewer costae, 1 or 

 where the intermediate elevated striae are few in number, or even often wanting, especially 

 in young specimens ; thus have been found undoubted C. Egnabergensis with only sixteen 

 costae, while others have thirty-eight on each valve. I do not, however, pretend to 

 dispute the existence of a distinct form under the name of costata, having well-charac- 

 terised specimens of it from the Cretaceous beds near Valogne ; but none of the British 

 shells which have come into my hands authorised me to admit the two species, nor do the 

 figures given of C. costata in Mr. Dixon's work entitle me to decide the question. The 

 manner in which this species was attached is also very remarkable ; in general, as in fig. 8, 

 it seems to have been simply fixed by a very small portion of the summit of its apex to 

 slender corals or bryozoa, or other branched bodies ; sometimes, as in fig. 9, its attachment 

 extended along the delicate coral from the vertex to the margin on one side only, interrupting 

 and indenting the costae ; in other and rarer cases, when attached to rocks, flat objects, 

 or shells, its fixed surface was much larger, and after minute examination of what takes 

 place in many other species, as we have described under the head of Th. Wetherellii. I 

 do not see reason for separating those specimens, figs. 13 and 14, attached by the greater 

 portion of their surface on Spatangus, a part of the costated portion rising all round. The 

 internal, muscular, and other impressions do not present differences of any value, from 



1 Sowerby is the first describer of C. costata, which he illustrates in No. 12, fig. 6 of his 'Genera of 

 Shells,' stating that he found it at Orglandes, (near Valogne, in France,) but does not mention having 

 discovered it in England. He characterises thus his species : " Cr. valvula superiore costis prominentibus 

 radiantibus octo ad quindecem." In the same number and plate, fig. 3, he figures a small Crania, fixed by 

 the greater portion of the attached valve to an echinus, stated to be from the Chalk of Norfolk, and which 

 he supposes to be C. Parisiensis. This is, however, a mistake : it belongs to C. Eynabergensis, and is 

 similar to the one I have figured, PL I, fig. 13. 



