JUKES BROWNE : SYNOl'SIS OF THE VENElilD^. 79 



I have made a careful investigation of the shells which have 

 hitherto been included in the genus Tapes, with the result that 

 I propose its division into two genera and the transference of the 

 T. pullastra group to the genus Venerupis. The reasons for this are 

 discussed under the head of Tapes. 



Genus Venus, Linnneus. 



Animal with frilled or fringed mantle-margins. Siphons rather 

 short and united for half their external length or more. Foot 

 lingtiifonn, thick or compressed, often extensile. 



Shell oval or sub-trigonal, more or less inequivalve. Lunulo and 

 escutcheon generally well defined. Sculpture concentric or cancellate. 

 Hinge-plate thick, with three divergent teeth in each valve, the left 

 I)osterior being long, narrow, and adherent, or adjacent to the 

 nymph. Pallial sinus small. In the right valve the posterior dorsal 

 margin is always grooved, but in the left there is seldom any groove. 

 Ventral margins crenulated. 



8ul-(jenera. 



Venus (s.s.), Lamarck, 1799. Type, V.mercenaria,\A\\xi, Synonym: 

 Mercenaria, Schunuicher, 1817. 



Shell ovate, convex, solid. Sometimes nearly smooth, sometimes 

 ornamented with thin, concentric lamellae and by faint radial striation 

 ou the posterior side. Teeth not widely divergent, not occupying 

 more than a right angle; left anterior straight, right posterior and 

 both medians generally grooved. Pedal scar separate from tlie 

 adductor, with a thread-like cliannel between them. Pallial sinus 

 triangular. 



Tliis group is restricted to the coasts of iS'ortli America and Japan ; 

 it includes V. canipechiensis, Gmelin {= morto7ii, Conrad, and 

 fulyurayis, Tryon), V. hnnicotti^ Dall, V. apodema, Dall, and 

 V. stimpsotii, Gould. Geologically it dates from the Oligocene, 

 and several species have been described by Conrad and Dall from 

 the Miocene and Pliocene of the United States. 



Chione, Megerle, 1811. Type, Ve7ius cattcellaia, Lam. 



Shell oval or sub-trigonal, oblique or sub-equilateral. Sculpture 

 always comprising concentric and radial elements. Hinge-plate 

 short, teeth becoming solid and entire with growth, but both medians 

 grooved when young, each set generally widely divergent. 



Section Chione (s.s.). Shell oblong or obliquely trigonal, inequi- 

 lateral, umbones prominent. Sculpture cancellate. Lunule and 

 escutcheon always well defined. Pallial sinus small and angular. 

 Pedal scar confluent witli that of adductor. Marginal crenulation 

 sometimes obsolete posteriorly. 



This section includes gramdata, Gmelin, pectorina, Lam., siib- 

 rostraia, Lam., cremdata, Sow. ( = puhera, Val.), grata, Say 

 {= histrmiica, Sow.), utidatella, Sow., succincta, Val., ptdicaria, 

 Brod., amathusia, Phil., gnidia, Brod. & Sow., asperrima, Sow., 

 columhiensis, Sow., suhrostrata, Lam., compta, Sow., and stiUchbunji, 



