80 PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



Gray. These are all American species except the last, which is 

 a New Zeahvnd shell. 



Section Timocle.a, Brown. Type, Venus ovafa, Pennant. 



Shell oval and nearly equilateral, the ninbones being generally 

 sub-central and not prominent. Sculpture cancellate, and the radials 

 sometimes stronger than the concentric ribs. Hinge-plate straiglit, 

 and the anterior teeth directed forward so that there is a wide 

 divergence. Nymphs high, and rather short. Pallial sinus obtuse or 

 rounded. Pedal scar separate from the adductor. Valve-margins 

 strongly crenulated all round. 



This section includes the following species — lacfopus, Lam., gaUinnla, 

 Lam., australis, Sow., costeUifera, Ad. & Rve., scalra, Wood, 

 striatissima, Sow., marica, Linn., recognita, Smith, aralcanensis, Sow., 

 snbnodulosa, Sow., siamensis, Lynge, tntcra, Pilsbry, imhricata, Sow., 

 lionata. Smith, ^;//^w;Yer?, Lam. The only American species known to 

 me which can be referred to Timoclea (as above defined) is pijgmcea, 

 which has an obtuse sinus and a separate pedal scar, though it is far 

 from being equilateral. 



Anoinalocardia, Schum., 1817. Type, Venus flexuosa, Linn. 



Synonyms : Triquetm, Anton after lUainville, 1818; Cryptogramma, 

 Morch, 1853. 



Shell trigonal, convex, posteriorly attenuated and angulated. 

 Sculpture mainly concentric, in broad rounded ribs crossed by finer 

 radial riblets. Teeth solid and widely divergent. Nymphs rugose. 

 Pallial sinus very small and sometimes obsolete. Pedal scar opening 

 narrowly into that of adductor. 



This is a small section only, including the species j?^j;?/om (Linn.), 

 brasiliana, Gmelin [ = macrodon^ Hanley), cuncimeris, Conrad { = rosfrata, 

 Sow.), subimbn'cata (Sow.), subnigosa (Sow.), imella (Pfeilfer), and 

 leptalea (Dall). All these, except the type, are American species. 

 Dr. Dall regards Venus squamosa, Linn., as an Anomalocardia, and 

 separates it as a section under the name of Anomalodiscus, but in my 

 opinion both it and subrostrata, Lam., belong to the typical section of 

 Chione, for I see no diff'erence except in shape. On the other hand, 

 Venus impressa, Hanley, has smooth ventral margins as well as smooth 

 nymphs, and is consequently a remarkable exception to the crenulated 

 margins of the genus. It might be regarded as a section with the 

 name of Crgptonema, in allusion to the concealment of the radial 

 striation along the margins. 



Clausinella, Gray, 1851. 



Synonyms : Circomphalus, Morch, 1853 (no type specified) ; Anaifis, 

 Romer, 1857 (in part), not of Duponchel, 1829. 



Shell with dominant concentric sculpture of strong ribs or ridges, 

 radial striation being absent or obscure. Teeth widely divergent and 

 solid in the adult, though the medians are often feebly grooved in 

 young shells. Lunule and escutcheon well defined, but the latter 

 more marked in the left valve. Nymphs striated and sometimes 

 rugose. Pallial sinus very small, angular or rounded. Pedal scar 

 very narrowly connected with that of adductor. 

 ClmisineUa, s.s. Type, Vefins fasciata, Da Costa. 



I 



