172 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 109 



The specimen from Point Barrow is definitely the sarsi and not 

 the gouldi form, being as long as high and evenly rounded on the 

 anteroventral border. 



Distribution: T. flexuosa, including the forms sarsi and gouldi, 

 occurs from Point Barrow south to San Diego, Calif.; in the western 

 Atlantic it occurs as far south as Connecticut; it is widely distributed 

 in the eastern Arctic, extending along the coast of Europe and into 

 the Mediterranean. The form gouldi has been reported from Bering 

 Strait to San Diego and from Greenland to Connecticut; Iceland and 

 Europe. Forma gouldi occurs on both our east and west coasts, 

 and forma sarsi occm's at Point Barrow. 



Genus Axinopsida Keen and Chavan, 1951 



Axinopsida orbiculata (G. O. Sars, 1878) 



Plate 20, figure 2 



Axinopsis orbiculata G. Sars, 1878, p. 63, pi. 19, figs, lla-d. — Soot-Ryen, 1939, 

 p. 14, pi. 1, fig. 7. 



A single specimen, measuring 3.2 mm. long by 3.4 mm. high, was 

 dredged at 120 feet on Aug. 8, 1949. 



Other material examined: About 34 specimens from localities 

 ranging from Cumberland Gulf to off Cape Cod, Mass. ; also over 20 

 specimens of the var. inaegualis Verrill and Bush from Nova Scotia, 

 Maine, and near Cape Cod. 



Discussion: This species is higher in proportion to its length than 

 A. viridis Dall, which some authors have suggested may be synony- 

 mous with A. orbiculata. In the latter the concavity in front of the 

 beaks is greater and the posterodosal margin slopes more rapidly than 

 in A. viridis. The ventral margin of A. viridis comes to more of a 

 point than in A. orbiculata. However, these differences are not 

 marked and further study may shov/ that A. viridis is only a variety 

 of A. orbiculata. 



Distribution: Madsen (1949) says that A. orbiculata is widely 

 distributed in the Ai'ctic; on the east coast of America south to Cape 

 Cod; off Norway to just south of Lofoten, and north of the Hebrides. 

 A. orbiculata is new to Alaska and the Pacific area of the Arctic. 



Family Ungulinidae 



Genus Diplodonta Bronn, 1831 



Diplodonta aleutica Dall, 1901 



Diplodonta aleutica Dall, 1901, p. 820, pi. 42, fig. 3. 



A single specimen of what is probably the very young of this species 

 was taken at 741 feet on Aug. 17, 1949; it measures 2.5 mm. long by 

 2.3 mm. high. 



