PELECYPODS 451 



with purplish rays arranged in various groupings ; over all is a glossy 

 epidermis. The hinge-teeth are very strong, and a prominent anterior 

 lateral tooth on the left valve is noticeable. There is an external liga- 

 ment; the pallial sinus is well marked, but not very deep. (Plate 

 LXXXIIL) 



GENUS Chione 



There are three species on the west coast. This genus is 

 very closely allied to Venus, and is considered by many to be 

 only a subgenus of the latter. All three species are white, solid, 

 heavy shells which exhibit the same scheme of sculpturing, 

 namely, numerous longitudinal ribs crossed by larger and less 

 frequent concentric ridges. 



C. simillima is shaped almost exactly like the east-coast Venus can- 

 cellata, but its concentric ridges are very numerous and sharp. There is 

 a strongly marked cordate lunule, and hardly any pallial sinus. Length 

 one and a hah 3 to two inches. (Plate LXXXIIL) 



C. succincta has fewer concentric ridges and has a large lunule. 

 There are purple zones within and touching the heavy cardinal teeth. 

 Length two and a half inches. (Plate LXXXIIL) 



C. fltictifraga has broad but flatter or well-rounded (not sharp) con- 

 centric ridges, no lunule, a small ligament, a fairly deep pallial sinus, 

 and a finely crenulated margin (within) all around the valves, except 

 when interrupted by the hinge ligament. The shell is solid and shining, 

 and marked by deep-purple zones within. Length one to two inches. 

 Found in southern California. 



GENUS Tapes 



This is a prominent genus of the Venendce. Its chief feature 

 is the total want of lateral teeth. There are several large species 

 in California. 



T. staminea, T. laciniata. These are the most noticeable species. 

 The former is sold in the San Francisco markets as the " hard-shell clam." 

 The shell of this species is from two to three inches in length and of 

 somewhat less height, rounded, and heavy. The sculpturing consists of 

 radiating ribs traversed by strongly marked growth -lines. The teeth 

 are strong, and the pallial sinus is deep. T. laciniata is much like the last, 

 but its surface is reticulated by a crisscross design that is very striking. 

 Ic also has a deep pallial sinus. These two species are of Southern range. 

 They burrow in gravelly places, among stones, between tide-marks, and 

 their presence may frequently be detected when walking along the beach 

 at low tide by seeing a sudden jet of water ejected from a little hole in 

 the mud or gravel. The animal, becoming alarmed at the approach of 

 something, suddenly snaps shut its valves, and thus forces out some 

 water through its siphons. The foot is very strong and often byssifer- 

 ous in this genus. (Plate LXXXIIL) 



