NO. 2 ROST: THE FAMILY ARCIDAE 199 



Holotype: San Diego Natural History Museum. Type coll. cat. no. 



11389. 

 Remarks: Although this species was rather recently described, it seems 

 to be common. Previously it has supposedly been confused with Anadara 

 {Larkinia) multicostata (Sowerby). The subgeneric placement of 

 Anadara reinharti is questionable. Small specimens are more like Cune- 

 arca, while very large ones are close to the Larkinia group. Reinhart 

 (1943) referred it to Scapharca, a placement followed here, though it 

 is not satisfactory. The specimens here referred to A. reinharti are 

 rather variable, a circumstance not common in the genus Anadara, al- 

 though some variation in this species has previously been pointed out 

 (Hertlein and Strong, 1943, p. 157). Possibly the group should be 

 divided into several species, but more knowledge of it will be necessary 

 before this can be done. Only small specimens were hitherto reported 

 under the name A. reinharti; thus we find that the type, which was 

 about the largest specimen reported, has a length of only 27.7 mm. 

 However, the present material includes samples with much larger speci- 

 mens (about 40 mm), one sample (773-38) containing 32 large speci- 

 mens, the largest of which measures 45.5 mm in length, 40.4 mm in 

 height, and 37.7 mm in diameter. The whole sample is preserved in 

 alcohol. One very large specimen (PI. 13, fig. 19), referred somewhat 

 doubtfully to A. reinharti, measures 75 mm in length, 58.5 mm in 

 height, and 59.5 mm in diameter; and has 31 ribs. The usual number of 

 ribs in this species varies between 26 and 29. The ribs on the left valve 

 are nodulose on the anterior and middle part on young shells and also 

 on the anterior part of the right valve. On older shells, the ribs become 

 grooved, especially on the left valve. Two to four grooves on the ribs 

 may be observed. The ribs on the left valve are broader than those on the 

 right and the interspaces are furnished with thin transverse ridges. In 

 some specimens the ribs may be smoother, and the breadth is also vari- 

 able. They are furnished with small pits as in A. multicostata. In small 

 specimens a faint groove or depression may be seen on the umbones. 

 This groove is sometimes colored with reddish-brown, and appears as a 

 colored line across the umbones. Other parts of the shell are sometimes 

 stained with reddish-brown also. 



A concavity on the posterodorsal margin distinguishes it from Ana- 

 dara {Larkinia) multicostata, and there is a slight convexity on the 

 posterior part of the ventral margin. Young A. reinharti is also more 

 elongate than A. multicostata and has a larger number of chevron-shaped 

 grooves on the ligament than has the latter species. A specimen of A. 



