294 CRETACEOUS PELECYPODA 



bein"" directed backwards, the cartilage pit posterior to it small and very oblique, 

 the posterior lateral tooth also small in the left, and almost obsolete in the 

 right valve ; the lunula is deeply excavated. The cretaceous Cmsmlella macro- 

 donta, Sow., may be considered as the type of this section. Deshayes (Paris 

 fossils) figures several eocene species. I do not know whether any of the recent 

 species show a similarly strong divergence of the hinge-teeth, but their form is 

 fully represented by such species as C. Jclngicola, Lam. 



Most of the recent and many of the tertiary species of Crassatclla have the 

 cartilage pit rather large and almost perpendicular below the beaks, the cardinal 

 tooth adjoining the pit in the left valve being smaller than the anterior tooth, while 

 the reverse is the case in the older species just pointed out. The lunula is 

 also only slightly or hardly at all excavated. I was first inclined to propose for the 

 older forms a separate name, but I find among the eocene species so many middle 

 forms that it would be impossible to define the division Avith any sufficient accuracy. 



Mr. Conrad seems to have settled the question very rapidly ; he proposes for 

 d'Orbigny's Crass. VincUnnensis (non VindiemensisJ , which is of the same type as 

 macrodonta, the new generic name Fachytheerus. I cannot see, as already stated, 

 sufficient ground for this generic distinction, though the separation may suit 

 Mr. Conrad's views better than those of any other conchologist, (see Am. Jom-n. 

 Conch., V, p. 47). Another cretaceous form was called (ibid. p. 48) by the same 

 author Scmihula ; its type is ^S*. per^^^ayja, being in every respect similar to the 

 recent Crassatella radiata, of which I have noted the description of the animal. 



List of cretaceous species. 



Fti/chowya (see Piet. and Camp., Pal. Suisse, 4™ ser., 3™'= part., p. 357). 



1-3. — Pt. Robinaldina* Germani, and neocomiensis. 



4. — Pandora aqroivalvis, Deshayes, (Mem. Soc. GeoL, v, p. 4, pi. 3, fig. 1 ; Crassaiella idem, 

 d'Orb.), can hardly be a Pti/chomi/a j there is no particular reason to be given why it could not be 

 a Pandora, but it may possibly be an Anlhonya, or perhaps a Remondia ( TniGoyiD^E ). 



5. — Crassatella Cornueliana, d'Orb., (Pal. frau9. eret., iii, p. 74, &c.,) is an Anlhonya. 



6-7. — Plych. solita, d'Orb., sp., and Pt. Buchlana, Karsteu, are from New Granada and 

 Columbia. 



8. — Anlhonya cultriformis , Gabb, see p. 293. 



Craasatella (see Pict. and Camp., 1. cit., p. 346). 



9-1 '2. — C. Saxoneli, Sal/audiafia, Fiziana, and inornala are all imperfectly known. 



13. — C. Galliennei would rather seem to be a Plychomya than a Crassatella. 



14-30. — Crassatella Guerangeri, (? Plychomya ), Ligeriensis, Vhidinnensis , (vide Gueranger, 

 Album paleont. de la Sarthe, 1867, pi. xvi,) sub-giljbosula, Neplinii, macrodonta, Austriaca, 

 Marrotiana, orbicularis, Galloprovincialis, Normaniana, Bufrenoyi, arcacea,f rugosa, Bosquefiana, 

 hellica, pisolithica. 



31. — C. calceiformis, Miiller, (Pet. Aach. Krcidef. Snppl., 1S59, p. 13, pi. vii, fig. 15,) is 

 a rather elongated form, and may belong to Anlhonya. 



* See also Cmss. comjdicafa, Tate, (Quart. Jouru. Geo!. Soc, Loud., 18G7, xxiii, p. IGO,) from the so-called 

 Jurassic deposits of South AiVica. 



t C. jmrullela, AUh, vide Trapezium, No. 109, p. 195. 



