398 CRETACEOUS PELECYPODA 



however, the genus from all 0»STi2jG'^iCii'^i, and as there is an anterior muscular 

 scar indicated in most of the 3IYTILACEA, the classification of the genus may he 

 more correct in this j)lace. If this should not he the .case, the only other classifica- 

 tion admissible would be near Myochama (see p. GO) in the Anatinid^ (sub-family 

 pandorinjeJ. 



30. Vulsella, Jjam., 1799. Sub-equivalve, modcTately tumid and solid, higher 

 than long, and sometimes ventrally gaping at the edges, with pointed or incurA'ed 

 more or less approached beaks, which contain internally the ligamcntal pit, its 

 margins being generally considcral)ly thickened on both sides ; muscular scar sub- 

 central, faint above, more marked at its lower edge ; outer surface fibro-lamellar, 

 finely scabrous or radiately ribbed ; type, V. lingulata, Linn. A list of the eighteen 

 recent and about eight tertiary species is given by Munier-Chalmas (Bull. Soc, 

 Normaudie, viii, p. 102, et seq.). Species from mesozoic and older deposits are 

 doubtful. 



31. 31((lleiis, Lam., 1799. Sub-equivalve, narrowly elongated, and often 

 twisted ; hinge area long, internally thickened, with distant beaks, more or less pro- 

 duced on either side into a long narrowed wing, ligamcntal pit extending somewhat 

 internally, a byssal sinus in front and very close to it ; muscular scar somewhat 

 irregularly elongated, placed some distance from the cartilage jiit; type, 31. vitlgaris, 

 Linn. Pteeve (Iconica, xi,) refers thirteen species to this genus. No fossil species 

 are known with sufiicient certainty. 



List of cretaceous species of Aviculid^. 



a. AVWUUNyE, (vide genus Acicala, in Pictet's Mat. Pal. Suiss., V™« ser., 4™' part., p. 70. 



1. — A. valantjiensis, P. and C. ; in furm closely resembling' Acditodesma, Sandb., but appa- 

 rently without any of the peculiar hinge-ribs which characterize this genus. 



2-3. — A. Cariero7ii and CoUaldina, d'Orh. 



4. — A. Sowerhyaria, Math., belongs to the sub-genus Meleagrina. 



5. — A. Cornueliana, d'Orb., ( =^ salradiata, Desh.,) is an Oj-ytoma, a suh-geniis of Pseiido- 

 7/1 Olio/ is. 



6-8. — A. Neoconiensis, Cott., and Suncfa-crucis, Piet. and Camp., and pectin fi//i, Sow. 



9. — -A. sub-dejiressa, d^Orb., ( = dejiressa, Forb.,) closely resembles A. auomala, both of which 

 have the external shape of recent Crenatulce. 



10-14. — A. (iptien-n-i, Rauliiiiana, sub-plicata, Cenomanietisifs and iaterrvpta, d'Orb. 



15-16. — A. aaomula* Sow., and Eolis, d'Orb., have, as already noticed, the form of some 

 recent Crenatulce. 



17. — A. Monioniana, d'Orb. 



18. — A. gri/plueoides, Sow., is most likely an Ancella. 



19. — A. simulutii, Baily, belongs to O.n/foma, a sub-genus of Pseiidomoiiotin. 



20-22. — A. Nj/m and Perif/ordina, d'Orb., Carenfonensix, Coq., are not sufficiently well known; 

 the last may be an O.ri/toma, judging from tlie depressed form of its valves. 



23. — A. glabra, Reuss, is certainly quite a distinct species from A. anomala. 



24. — A. Neptuni, Goldf. I would be more inclined to regard this species as a Modiola than 

 an Avicula, but I have no specimens to compare. 



* Mem. Acad. IBoljjinuu, xxxiv, 1S70, Briart ct Coruct, Fussilcs de la moule de Bracijucgnies, p. 52. 



