Yol. 6^.~] OX FULLERs'-EAHTH BEACHIOPODA. 429 



referred to Smith's species, is quite different — it is a Fullers '-Earth 

 Rock shell. Davidson said that it camefrom the Inferior Oolite, but 

 this is an error. Douville, misled no doubt by Davidson, referred 

 to it as a Bajocian form. Douville saw the incorrectness of applying 

 Smith's name, which had been given to an already-named species, 

 to a shell that was distinct and from quite a different horizon. 

 Therefore he proposed the specific name ' subreticulata.' 



My colleague, the late J. F. Walker, died before he had sent me 

 his remarks on this fossil, but he had written, ready for sending, 



' we had better say that we accept Dietyobhyris subretiadata, of Douville, but 

 state that he is in error when he refers it to the Bajocian instead of to the 

 Fullers' Earth.' 



This was Mr. Walker's view as early as 1877, as will be seen by 

 referring to Davidson's ' Monograph ' — I mean that he held that 

 Dictyoihyris coarctata, Park, and D. reticulata, Sow., were distinct. 



Ornithella 1 cadomensis (E. Deslongchamps). (PI. XXYIII, 

 figs. 4a & 4 6.) 



1857. Bull. Soc. Liun. Norm. vol. ii, p. 343 & pi. iv, figs. 3-4. 



1873. E. Deslongchamps, in A. d'Orbigny's ' Paleontologie Francaise : Terrain 



Jurassique — Brachiopod.es ' p. 312 & pi. lxxxviii, figs. 8-9, pi! lxxxix, tig. 1. 

 1878. Davidson, ' Monogr. Brit. Foss. Brach.' Suppl. (Palseont. Soc.) vol. iv, p. 170 & 



pi. xxii, fig. 9; young specimens, pi. xxiv, figs. 14 & 15. 



Diagnosis. — Shell ovoid, longer than wide, widest near the 

 centre of the shell, from which it tapers towards the straight anterior 

 margin. Shell-surface smooth, though marked with concentric 

 lamellae. Yalves inflated, but the dorsal valve is somewhat com- 

 pressed near its beak ; it shows a dark line, extending nearly to 

 the anterior margin, which indicates a long median septum. The 

 ventral valve is convex, gradually sloping towards the rounded 

 lateral margins. Beak straight, but incurved at its extremity, and 

 terminated by a small circular foramen, which is separated from the 

 dorsal valve by a small deltidium in two pieces. Beak-ridges sharp 

 and concave ; hinge-line curved. 



The young specimens are subcircular, and less globose than the 

 immature forms of Ornithella ornithocepluda. 



B-emarks. — Ornithella cadomensis (E. Desl.) differs from the 

 0. ornithocejjhala of the Fullers' Earth in being much more inflated, 

 in the beak-ridges being more sharply-defined, in the greater 

 distance of the beak from the umbo, and in being marked with 

 concentric lamellae. 



0. cadomensis was first found in England in the Fullers' Earth 

 of ' Charlcourt', near Bath. There are slight differences between the 

 Continental shell and the British. In the latter the lamellae are 

 less pronounced, and the shell is somewhat wider. 



Deslongchamps has separated the shells obtained from the 



i Deslongchamps gave the subgeneric name ' Ornithella' 1 before ' Microthyr is,'' 

 These have been united by Hall & Clarke and called Microthyris, but they give 

 no reason for so doing ; see their ' Introduction to the Study of the Brachiopoda ' 

 pt. ii, 13th Ann. Eep. State Geologist N.Y. for 1893, vol. ii (1894) p. 884. 



