NO. 2 ROST: THE FAMILY ARCIDAE 201 



age, and in a specimen 29.8 mm long, one groove reached before the 

 umbo. Sometimes the shell is stained with light reddish-brown, especially 

 on the umbones. The periostracum is bristly in the interspaces between 

 the anterior and posterior ribs, but shell-like in the median part. The 

 posterior and anterior rows of teeth overlap. Maur>^ (1922) reports a 

 specimen with a length of 35 mm, which seems to be the maximum 

 recorded length of this species. Anadara cumingiana should possibly be 

 referred to the subgenus Rasia Gray. 



Occurrence: A. cumingiana is taken from 5 to 50 fms, although it 

 commonly occurs deeper than 20 fms. Sand, mud, or sandy mud are the 

 common components of the bottom in which it lives. The Allan Hancock 

 material extends the distribution south to Isla Salango, Ecuador. 

 Distribution: Bahia de San Luis Gonzaga, west coast of Gulf of Cali- 

 fornia (29° 50' N), to Isla Salango, Ecuador. 



Anadara (Scapharca) biangulata (Sowerby) 1833 



Text-figs. 86, 87 a-c 



Area biangulata Sowerby, Proc. Zool. Soc. London, 1833, p. 21. 

 Syn.: fArea gordita Lowe 1935. 



Fig.: Lowe, 1935, PI. 1, f^g. 1; Reinhart, 1943, PI. 12, figs. 10-11. 

 Type loc.: Atacames, Ecuador; 7 fms. 

 Holotype: British Museum? 



Remarks: It is very probable that Anadara biangulata and Area gordita 

 represent the same species; they were so considered by Hertlein and 

 Strong (1943). Sowerby's description is short and an illustration of the 

 type was not given. Sowerby, who had a single specimen, described it 

 among the equivalves. A complete specimen in this collection, which 

 measures 25.6 mm, is very distinctly inequivalve, with the left valve 

 overlapping the right ventrally. Reinhart (1943) placed Anadara 

 gordita in Anadara s. s. because of the similar sculpture on both valves. 



Two V-shaped ligamental grooves are present behind the umbones in 

 a specimen 25.6 mm long, as shown in text-fig. 86. The stippled area is 

 covered with ligament, and the elastic bands across the V-shaped areas 

 are indicated. The rows of teeth overlap as in Anadara concinna. The 

 sculpture in the interspaces between the ribs is also similar in the two 

 species. The figure by Reinhart (1943) gives a very^ good picture of the 

 sculpture. Small specimens are more elongate in shape than larger ones. 



This species should probably be referred to subgenus Rasia Gray. 

 Occurrence: Hertlein and Strong (1943) report it from 12 to 61 fms. 

 Muddy bottom is most common, also sand, crushed shells, etc. The only 



