MOORE — ON NEW BRACHIOPODA, ETC. 



91 



ridge passes round the front and sides of the dorsal valve, until it 

 reaches the dental sockets. It is without a central septum, nearly 

 always present in other species, the only ornamentation within the 

 ridge being numerous punctuations. 



Obs. — This shell is very numerous in the Coral Rag of Lyneham, 

 associated with the T. ornatum and the T. triangularis. I have been 

 unable to trace any passage into either of the above species, other- 

 wise it might have been considered a young stage of one of them. As 

 it is altogether different in character, and as the shell, though so 

 minute, is very persistent in its form, I have ventured to give it the 

 above specific designation. 



Thecideum triangularis. D'Orbigny. 



This species has hitherto been noticed only in the Middle and 

 Upper Lias and the Inferior Oolite. I have now obtained it from 

 the Lower Lias of Keynsham, which is the oldest formation in which 

 it has yet been found. It then passes through the beds above men- 

 tioned, and is very common— -attached to Lima, Ostrea, and other 

 shells — in the Fuller's Earth of Combehay, near Bath. It occurs also 

 in the coralline bed of Hampton Cliffs, and again in the still higher 

 zone of the Coral Rag of Lyneham. ]STo other species of Brachiopod 

 has yet been known to have attained so long a range as is indicated by 

 the above facts. Its uninterrupted passage through so many forma- 

 tions points out the absence of any considerable climatal or other 

 changes during the deposition of the beds in which it is found. 



I have evidence of the presence of several other species in the 

 Inferior Oolite of Dundry, one very nearly approaching the T. Des- 

 longchamjpsii, Dav. ; but as only separate valves have been found, 

 it will be unsafe at present to say more respecting them. 



Crania. Retzius. 

 Crania canalis. Moore. PI. ii., figs. 8 — 10. 



Shell subquadrate, usually flattened, at other times more or less coni- 

 cal. The outer surface of the young shell exhibits a few coarse striae, 

 which continue to the margin of the valve. In the adult these 

 become much more numerous, many of them passing as narrow 

 spines, some distance beyond the outer margin of the shell. The in- 

 terior of the valve is concave, showing two pairs of muscular im- 

 pressions, not strongly marked ; the anterior pair curving upwards 

 towards the posterior, which are rounded and larger. When viewed 

 from the inner side the valve is seen to be surrounded by a flattened 

 ridge, which is continued outwards in long spinose expansions, which 

 are famished with narrow longitudinal grooves, or canals, through 

 the whole of their length. 



Obs. — This is one of the most beautiful species of this interesting 

 genus of shells. It is from the raggy beds of the Inferior Oolite of 



VOL. IV. N 



