CHAMA, CARDIUM AND VENUS 65 
of the last, but are generally larger and have two 
separate siphon tubes, while in Pisidium they are 
united. This species is found in Cal., Utah, and 
Oregon. Length of shell half an inch or less. 
Sphaerium patéllum, Gld., the Plate-shell. Shell 
very thin, smoother and less robust than the last, 
and half the length. Specimens from Sonoma Co., 
Cal. 
Sphaérium occidentale, Prime, the Western 
Sphere-shell, is nearly cireular in outline, with a 
shell quite smooth and firm, robust, same size as 
the last. From Weber Canyon, Utah. 
Sphaérium dentatum, Hald., the Toothed Sphere- 
shell. Hatchet-shaped, when viewed from the side, 
but bulged at the umbones and cordate at the ends. 
Epidermis olive green, glossy, shell 6 mm. long. 
From the Chehalis River. 
We now come to the Venaracea, a sub-order in- 
eluding many of the most interesting shells to be 
found along our coast. The first one to describe is 
named Dosinia ponderosa, Gray, the Heavy Do- 
sinia. Its home is near the equator but it is found 
northward from Peru to San Pedro Bay. The shell 
is nearly circular, about four inches in diameter, 
pure white internally, but creamy brown on the out- 
side. Itis very smooth, save for concentric lines of 
growth, and the deep lunule is heart-shaped. The 
valves are thin at the edges, but very thick and 
heavy in the older parts. The pallial sinus is V- 
shaped, and the ligament is external. 
Transennella tantilla, Gld., the Little Transen- 
nella, has a shell ranging from % to % of an inch 
