CYPRIDINA. 179 



alive, and resembled, he says, " those small insects called 

 in France puces d'eau." The body of the animal Avas 

 contained in a little shell, which was transparent, and 

 resembled in form an almond cleft on one side, and 

 notched at the superior part. The animal, besides several 

 organs, which he shortly describes, had, he remarks, " a 

 large foot, armed with a toothed talon, resembling that of 

 i\\e, puce d'eau, and destined for the same uses, being a 

 kind of rudder, which enables the insect to move about 

 with swiftness." Such appears as yet to be the whole 

 amount of our knowledge with regard to the habits of this 

 genus. 



1. Cypridina Mac Andrei. Tab, XXII, fig. 1 a-^. 



CYmiDiNA Mac Andrei, Baird, Ann. and Mag. Nat. Hist., 2d series, 

 i, 21, t. 6 B, f. 1-7, 1847. 



The shell or covering is of an oval shape, the two ex- 

 tremities prolonged into sharp points ; that of upper 

 extremity curved and projecting forwards, and a little 

 upwards, that of inferior extremity projecting a little back- 

 wards. The whole surface of the valves is dotted over with 

 small points, and on their anterior edge, near the upper 

 extremity, they are deeply notched. The eyes are ovoid- 

 shaped, and areolar. 



The first pair of antennae (t. XXII, f. 1<?) is of con- 

 siderable length, and consists of five articulations. The 

 basilar joint is the longest and largest ; the second is of 

 nearly equal size, and armed on its external edge with 

 five or six short setae ; the third is the shortest ; the fourth 

 is about twice the length of the preceding, and like it 

 sends off" two or three short setae at the extremities ; and 

 the fifth, or terminal, has at its extremity six or seven long 

 setae, which are not plumose. The second pair of antennae 

 (t. XXII, i.\c; t. XXIII, f. Ic) is about two thirds 

 the size of the first pair, and is divided into four articu- 

 lations. The first, or basilar joint, is stout, and of consi- 



