194 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 20 



Unfortunately, this unsatisfactory arrangement must also be followed 

 in the present paper. To make a more natural and correct system, species 

 from all regions of the world would have to be carefully studied. How- 

 ever, the present material may give some indication of relationships. The 

 arrangement of the abdominal sense organs is shown by Heath (1941) 

 to be a good character for generic classification. But of course many 

 characters must be studied and used together for proper determination. 

 As shown in text fig. 90c, Anadara obesa (Sowerby), which has always 

 been placed in Scapharca because it has smooth ribs and is inequivalve, 

 has the structure of the anal region like that of A. {Cunearca) nux 

 (Sowerby) and A. {Cunearca) aequatorialis (Orbigny). The same 

 situation as in the species mentioned was found by Heath (1941) in A. 

 {Cunearca) chemnitzi (Philippi) (PI. 15, fig. 11), a Caribbean species, 

 and in A. {Cunearca) perlabiata (Grant and Gale) (PI. 14, fig. 6), 

 while A. {Cunearca) brasiliana (Lamarck) = incongrua (Say) (PI. 

 17, fig, 3), the type of the subgenus Cunearca, is different not only in the 

 aspect mentioned, but also in other anatomical structures (Heath, 1941, 

 pp. 304-305). None of these species, as far as I know, have any pigmenta- 

 tion on the mantle margins. 



A. {Scapharca) biangulata {?)Owtrhy) = gordita (Lowe), A. 

 {Scapharca) curningiana (Nyst) = concinna (Sowerby), and the 

 Caribbean A. {Scapharca) notabilis (Roding) = auriculata auct. non 

 Lamarck, seem to belong to the same group. Perhaps the subgeneric 

 name Rasia Gray 1857 (type, Anadara formosa (Sowerby), designated 

 by Stewart, 1930) ought to be used for these species. Anadara baugh- 

 mani Hertlein 1951 is also believed to belong to Rasia. Among similar 

 shell characters may be mentioned the wide flattened area anterior to the 

 umbones which is not covered with ligament (text-fig. 86). The two 

 species Anadara biangulata and Anadara notabilis (from Aruba), which 

 are both found in the Hancock collections, have the same arrangement 

 of eye-spots. The soft parts of Anadara curningiana are not at hand, and 

 Heath (1941) does not describe this character in his work. The ab- 

 dominal sense organs of A. biangulata are like those found by Heath 

 (1941) in two species of Anadara s. s. Heath also states that the three 

 species of Scapharca studied by him, A. curningiana, A. notabilis, and 

 A. transversa, have the Anadara s. s. type of abdominal sense organs. 



The subgenus Cara Gray (1857, p. 371, type Anadara aviculaefor- 

 mis (Nyst), designated by Stewart, 1930) is used by Hertlein and 

 Strong (1943) for Anadara emarginata (Sowerby). Reinhart (1935) 

 placed Cara as a synonym of Scapharca. The subgenus should perhaps be 



