PELECYPODS 445 
margin is striking. It has very fine cardinal teeth. Length two to 
three inches. 
M. baltica, M. proxima, M. tenta. The first two of these species 
are dingy in color, and are covered with a dirty-looking, thin epidermis. 
The first has a wide range to Norway and Scotland, and is exceedingly 
common all along our coast from Maine to Georgia. 
It occurs plentifully in the Hudson River above 
New York, and in all sandy or muddy bays. It is 
rounded in outline, while the next species (M. 
proxima) is more pointed posteriorly. When these 
species are buried in the sand their two long, slen- 
‘der siphons project above, one supplying the animal 
with a constant current of fresh water, and the other 
ejecting that which, having passed the gills and Macoma baitica, 
labial palps, is exhausted of its air and nutriment 
and contaminated by waste products. MV. tenta is 
white, with very fine lines of growth, and polished 
and shining within. It is warped posteriorly. Length 
three fifths of an inch ; height two fifths of an inch. 
FAaMILy DONACIDE 
Genus Donax 
The Donacide are represented upon our coasts by compara- 
tively few species, all belonging to the genus Donaz. The shells 
are under an inch in length, and have a peculiarly shortened an- 
terior portion; thus they are inequilateral. Their ventral mar- 
gins are finely denticulate. The pallial sinus is deep. There are 
two or three cardinal teeth and a variable number of laterals. 
D. variabilis. This little shell, the common Floridian form, exhibits 
every imaginable scheme of color-combination, and defies general or 
comprehensive description. Probably the most usual pattern developed 
is a bluish-white background with purplish radiating lines. Another 
is a pure-white foundation with red lines. The surface is striated longi- 
tudinally with excessively fine riblets. Length one half of an inch or 
slightly more. In Marchand April these shells are thrown alive in 
millions upon the Florida beaches. Each wave seems to be laden with 
them, and when the foaming waters of each spent breaker recede, the 
little shells lie still upon the sand for a moment, glittering like jewelsin 
the sunlight; then, with a sudden protrusion of the foot and a quick 
turn, they all disappear like a flash, buried in the sand before the next 
breaker strikes them. One must be very quick to catch these active lit- 
tle mollusks. (Plate LXXXI.) 
D. californicus. Professor Keep very aptly describes this shell, 
which is very common in California, as “short and stumpy, cut 
nearly square off at one end (anterior), and tapering to a rounded edge 
at the other.” The same description fits both this and the Floridian D. 
variabilis so well that the two forms may be one and the same species. 
