56 CALIFORNIA SEA SHELLS. 



back of the umbo. The hinge teeth are very 

 small, and the pallial sinus extends nearly the 

 whole length of the shell. Behind the ligament, 

 the shell narrows into a short, brownish wing. 

 The length varies from two to four inches. 



Macoma nasuta, Conr., PI. XV, Fig. 3, is a 

 very common species, reaching from Kamtschatka 

 to Mexico. It is abundant in San Francisco Bay, 

 and some of the large shell-mounds of the aborig- 

 inies, on the shores of that bay, are largely com- 

 posed of the valves of this species. It inhabi's 

 muddy flats, burrowing quite deeply, and 

 reaches the water by its two, small, red siphons. 

 The shell is smooth and thin ; the posterior part 

 is narrowed and twisted to one side. Tbe hinge 

 teeth are small, the ligament is external, and the 

 pallial sinus reaches to the forward muscular 

 scar. The common length is two inches. 



The Red-lined Sand-shell, Psammobia ruhro- 

 radiata^ Nutt., is a fine shell, represented in Fig. 

 4, 1*1. XV. The figure was drawn from a shell 

 found at Monterey, which measures two and one 

 half inches in length. The outside of the shell 

 is smooth and whitish, marked with broad, radi- 

 ating, red bands, much resembling the rays of 

 the setting sun. The inside is of a tine, glossy 

 white, like choice porcelain. Hinge teeth, small ; 

 ligament, external ; sinus, large. 



Sanguinolaria Nuttallii, Conr., is a southern 

 species. The shell is thin, rounded and flatten- 

 ed, covered with a glossy, dark brown epidermis, 

 beneath which may be seen radiating bands of 

 color. Ligament, laiye and external ; pallial 

 sinus, very large ; length, three inchos. 



