592 LIASSIC DENTALIID^. [Nov. I906, 



arma^i-hemera consists of cream-coloured, slightly ironshot lime- 

 stones. 



Moore referred this ' curious little shell ' with some doubt to the 

 genus Dentalium, but his diagnosis was perfectly correct. 



Quenstedt obtained specimens of the tube of a Dentalium, or of 

 some tubicolous annelid, which very much resembled it, from the 

 margaritatus-heds of Dorlbach, and figured and described it as 

 Serpula triedra (' Der Jura ' pi. xxiv. fig. 55), but admitted that 

 the three sides were flat and smooth like those of a Dentalium. 

 At a later page (329) of the same work he showed his uncertainty 

 as to the accuracy of the generic diagnosis, for he wrote : 



' In the Lias I find very few \JDenf edict], perhaps the Serpula triedra pag. 200 

 would be better named Dentalium on account of its smoothness.' 



Provisionally this fossil may be regarded as Dentalium trigonale, 

 Moore. This was also Tate's view, as shown by the note-book of 

 his in my possession ; but it should be noticed that Quenstedt's 

 fossil is a margaritatus-bed form, more equilateral, and probably 

 another species. 



As might be expected from the very brief description of Denta- 

 lium compressum given by d'Orbigny — that it is a ' species strongly 

 compressed, subcarinated, smooth' l — much difficulty has arisen in 

 identifying the form. 



Dentalium compressum, Terquem, is probably the same as my 

 D. subovatum (see p. 587) : for, as Terquem rightly remarks, 

 d'Orbigny's Dentalium is a Middle Liassic shell, while his came 

 from the ' gres infra-liasique de Hettange/ and has the same 

 range in time as D. subovatum. Terquem, in defence of his 

 acceptance of d'Orbigny 's specific name for his fossil, felt it 

 necessary to state that it was difficult to point out a specific 

 character in a shell belonging to a group subject to so little 

 variation. 



In 1869 E. Dumortier 2 complained of d'Orbigny's too brief de- 

 scription and wondered whether D. compressum could be the same 

 as Moore's D. trigonale, but he made no other remark. In 1875, 

 however, Tate concluded that this was actually the case, and re- 

 corded, in his list of fossils from the Eadstock Lias, 



' Dentalium compressum, D'Orb. (D. trigonalis, Moore). Two examples, 

 Camerton ; four examples, Eadstock, Munger, and Clan Down.' (Quart. Journ. 

 Geol. Soc. vol. xxxi, p. 504.) 



In order to endeavour to solve this problem I communicated 

 with M. A. Chenevrier, Assistant Palaeontologist at the National 

 Museum of Natural History, Paris, who replied [translation] : 



'D'Orbigny's collection contains only a single specimen of this species, 

 coming from Chalon-sur-Saone. It is a fragment of a calcareous tube, slightly 



1 'Prodrome de Paleontologie stratigraphique: Liasien' 1850, no. 135. 



2 ' Depots Jurassiques du Basin du Phone ' pt. iii : ' Lias Moyen ' June 1869 

 p. 160. 



