SYXOPSIS OF THE LUCINACEA—DALL. 789 



AXINOPSIS ORBICULATUS G. O. Sars, 1878. 



Greenland and Cunil)erland Sound, south to Casco Bay, Maine, lU to 

 30 fathoms; Arctic Ocean and northern Norway, 8 to 120 fathoms, 

 hut not on the Pacific side. 



A variety rnmji/alwYcrriW and Bush, 1898, found in 18 to 20 fathoms 

 from the Bay of Fundy to Cape Ann; is more quadrate, less orbicular, 

 and all the specimens examined are smaller than the adult ^1. orhica- 

 latus. A large proportion of all those dredged ])y the U. S. Fish 

 Commission, when compared with those from the high north, appear 

 to be immature. The forms referred to this species from the Pacific 

 coast as far as examined all belong to other species of the genus. 



AXINOPSIS CORDATA Verrill and Bush, 1898. 



Marthas Vineyard to Cape Hatteras, North Carolina, in 43 to 202 

 fathoms. 



Extremely close to those Thyasiras which have the proximal end of 

 the indented anterior hinge line slightly thickened. 



LEPTAXINUS MINUTUS Verrill and Bush, 1898. 



Off Marthas Vineyard, in 100 fathoms; easily identified by the dis- 

 tinct lateral laminae. 



LEPTAXINUS INCRASSATUS Jeffreys (as Axinus), 1876. 



Baffins Bay and North Atlantic, in 1,480 to 1,785 fathoms; north of 

 Ireland, in 1,180 fathoms. A variety ( ?) off' Culebra Island, West Indies, 

 in 3;t0 fathoms, Challenger expedition. 



J effreys's original type is figured as exhibiting denticulations which 

 probably liolong to a provinculum. His specimens in the U. S. National 

 Museum do not show it, but are evidently referable to Leptaxlnus. His 

 variety saccisa., however, is a distinct species of Axifiulns. 



Note. — The shell described by Reeve in 1850 as Lucina Jjarhaf a was 

 doubtfully referred to Cryptodon by E. A. Smith, in his report on the 

 Challenger bivalves. That gentleman now thinks this identification 

 questionable, as it was founded on a single imperfect valve which may 

 find a place in Lucina., properly so called. Both shells are probably 

 true Lucinas and the Challenger valve may be a drifted young specimen 

 of L. pldlipplarut Reeve. 



SPECIES OF THE PACIFIC COAST OF AMERICA. 



THYASIRA BISECTA Conrad (as Venus), 1849. 



Gulf of Alaska and Puget Sound, in 69 to 135 fathoms. Also in the 

 later Tertiariis of California as far south as San Pedro. 



This is Cyprina hisecta Conrad, 1865, and ConcJiocele disjuncta Gabb, 

 1866. It is the largest species of the genus, measuring up to 80 mm. 



