148 CEETACEOIJS PELECYPODA 



much of the form of a Tapes, the anteriors being large and sub-equal, as compared 

 with other forms of Vemis. However, in this respect, there seems to be a distinct 

 inclination to the form of the hinge of Venus rather than to that of Tapes. 

 Venus mercenaria, L., is the type of the sub-genus, and if the latter name Mer- 

 cenaria is applied sub-generically, the species ought to be called Venus \MerGenaria'\ 

 notata, Say, for it is certainly not desirable to have a repetition of one and the 

 same name as genus, or sub-genus, and species. 



Qb. Cryptogramma, Morch, 1853 (?). Shell inflated, cuneiform, posteriorly 

 more or less narrowly produced, anteriorly shortened and thick, outer surface gener- 

 ally with concentric lamellae and often also with radiating ribs, seldom preva- 

 lent over the former, which occasionally become almost obsolete in the middle ; 

 hinge with three elongated cardinal teeth in each valve, the anteriors being the 

 smallest. The type is V.flewuosa, Linne ; if we accept the sub-genus as possessing 

 any value in classification, we cannot exclude from it such species as V, pygmcea, 

 Lam., or V. scabra, Wood. H. and A. Adams state that there are only two 

 cardinal teeth in each valve, which does not seem to me to be exactly the case. 

 I have examined several species like V. macrodon, squamosa, sub-noclulosa, and 

 others, and I always found three cardinals in both valves, very distinct in the left, 

 but in the right one, the most anterior, usually is small, though always traceable. 



66?, CMone, Megerle v, Miihlf., 1811 (^=== Murcia, Bom., 1857). Shell ovate 

 or cordate, thick, concentrically lamellar or ribbed ; hinge with three sub-equal, 

 usually straight teeth in each valve; pallial sinus small, 'sometimes acutely trian- 

 gular, or almost obsolete. The Venus cancellata, Linn., (Gronov. ?) must be con- 

 sidered as the type of this sub-genus, representing the sub-ovate, strongly lamellar 

 forms. H. and A. Adams again state that there are only two cardinal teeth in the 

 left valve ; I have examined several species, and I find the posterior tooth is here 

 generally quite distinctly traceable and raised above the rest of the fulcrum ; it is 

 always shorter than this. The authors of the ''Genera" besides distinguish 

 four sub-genera undei;' the names of Circomphalus, Klein, Timoclcea, Leach 

 ChamelcBa, Klein, and Marcia, H. and A. Adams. Most of the species of the 

 .last sub-genus belong to Hemitapes of the tapesin^. Eomer (Mai. BL, vol. xiv), 

 divides the sub-genus Chione into four sections under distinct (generic !) names, 

 as 1, Omphaloclathrum, Klein C=AnUgona, Shuhm.,) with F. puerpera, reticulata 

 and others, some of which appear to be typical Venus as restricted ; 2, Leucoma, 

 Eomer, with V, grata, Say, granulata, GmeL, and others, which H. and A. 

 Adams refer to TimoclcBa; all have peculiarly granulated radiating ribs; 3, 

 Chamelcea, Klein, apparently in the same sense as stated in the '' Genera," with 

 F. gallina, Linn., (?) &c. ; 4, Ventricola, Pomer, with V, verrucosa, Linn,, &c. 



In 1857 (Krit. Untersuchung, &c.,) the same author sub-divided his Murcia 

 f= ChioneJ into Antigona, Chamelea, Leucoma, Anomalocardia f= Crypto gramma J, 

 and Katelysia. The last includes among others V. exalbida, Chem., and scalarina. 

 Lam., both somewhat of the Fullastra type and probably belonging to the 



T4.P:E8tNjE, 



