914 PELECYPODA. [Eulamellibranchia. 



tnincates it, the posterior lateral distinct, short ; left valve with 

 2 diverging cardinals, the anterior triangular, heavy, usually bifid ; 

 the anterior lateral tooth similar to that of the right valve, posterior 

 lateral obsolete. Ligament fairly long, external, the nymphse well 

 developed. Anterior adductor-scar long and narrow, the posterior scar 

 short and oval. Pallial line simple. 



Diameter Ant. -post., 29 mm. ; dorso-ventral, 27 mm. : thickness, 

 15 mm. 



Type in the British Museum. 



Hob. Bay of Islands ; near Little Barrier Island, in 20 fathoms ; 

 Channel Island, Hauraki Gulf, in 25 fathoms ; Auckland Harbour ; 

 Whangarei Heads ; Nelson ; Summer ; Dusky Sound, in 12 fathoms ; 

 Chatham Islands ; cfE Great Barrier Island, in 110 fathoms ; 

 Kermadec Islands (Captain Bollons). The type is from St. Vincent 

 Gulf. South Australia (Angas). Found also in Port Jackson. Tas- 

 mania, Ceylon. 



Remark. Lives buried in sand in deep water, and therefore only 

 obtained by dredging, or found washed up on the beach after heavy 

 gales. 



Fossil. Eocene to Pliocene. 



Var. Huttoniana, Vanatta, 1901. 



Lucina (Divaric.ella) Hvttoniana, Vanatta, Proc. Acad. Nat. Sci. Philad., 

 Feb. 1901, 184, pi. 5, f. 14, 15. 



Distinguished from the species by having a long narrow lunule, 

 more delicate texture, and lower beaks ; it is also much less globose. 



Altitude, 29-5 mm. ; diameter, 32 mm. ; thickness of right valve, 

 8 mm. 



Type in the collection Acad. Nat. Sci., Philadelphia. 



Hob. Auckland. 



Genus 3. MONTACUTA, Turton, 1822. 



Montacvta, Turton, Dithyra Brit., 1822, 58. Type : I/, subslriata, Mtg. 

 Tellimya, Brown, 1827. 



Animal with the gills on each side with only the direct and reflected 

 inner lamina developed ; hepatic glands arborescent, projecting from 

 the ordinary body-wall. 



Shell small, more or less transversely ovate, posterior end usually 

 shorter ; anterior part of the hinge provided, in the right valve, with 

 a naxrow lamina having a minute cardinal hook at the proximal end ; 

 the left valve with a similar lamina on which the hook is less prominent 

 or even absent ; external ligament obsolete, amphidetic, leaving no 

 traces on the shell ; resilium strong, internal, posterior, seated on 

 nymphs of which the right one is usually less strong ; the ventral 

 surface of the resilium, in the larger species, with a thin calcareous 

 deposit, often wholly absent and never forming a developed litho- 

 desma ; the distal portions of the laminae sometimes obsolete. (Dall.) 



