STATE GEOLOGIST. ' 99 



Description, etc. — General shape that of an elongate rectangular prism, or 

 sub-cylindrical. Carapace elongate oval, truncate before and behind, very trans- 

 parent, being obviously reticulated only near the anterior portion. 



Head large, obtuse in both vertical and horizontal aspect, furnished with a 

 projecting disc or plate on the posterior part of upper surface. Eye round and 

 rather large, red, with many cornese. 



Superior antennae are quite observable, being rather long and armed with 

 four bristles on the extremity. * 



Inferior antennae very large. The basal joint is cylindrical, very large and 

 fleshy, and wrinkled so as to appear many jointed. The two rami are unequal 

 and rather short. The outer ramus has three articulations. The first is short 

 and furnished with a minute spine. The second is longer and has three strong- 

 jointed setae on the inner margin, and a spine near its articulation with the 

 third, which is of nearly the same length, and has four setae on the inner margin, 

 three at the end and a small spine at the upper outer angle. 



The mner ramus has two unequal joints, the lower of which is much the longer, 

 and is furnished with a spine and a seta, while the second has four large-jointed 

 setae at the extremity. 



The labrum and mandible are similar to those of Daphnia. 



The feet are of six pairs, which are described as follows: 



The first pair consists of a main stalk of two joints, of which the first has four 

 setae, and the terminal (or "hand'') joint seven. The first joint also has two 

 branchial plates, of which the upper and smaller possesses nine or ten short setae 

 and one jointed and plumose filament, while the lower or main plate has about 

 thirty plumose setae. The second, third, fourth and fifth pairs are quite similar, 

 but the stout setae on the outer margin of the first joint are replaced by a trian- 

 gular plate and the branchial filaments are shorter. The sixth pair has three 

 articulations, each furnished with straight, stout spines, and is curved. The 

 abdomen has at its extremity two strong, curved claws, which have each three 

 spines on the basal half, and are dentate for the remainder of their length; it also 

 has two tubercles at the angle behind each of which bears a long seta. Between 

 the claws and these knobs are two rows of spines. 



The ovary contains in full grown females, about twenty young, which resemble 

 their parent from birth. 



The organ on the top of the head is used as a sort of sucker, by which the 

 animal adheres to water plants. 



Their motion is rapid and steady. The circulation of the blood can be seen 

 through the transparent walls of the body and head, as in the front part of the 

 head, where the minute, colorless corpuscles are easily seen coursing from above. 

 There appears to be a dorsal vessel just above the intestine in which these glob- 

 ules can be seen as they pass from behind forwards to near the juncture of the 

 carapace with the glabella of the head, where is an enlargement forming the 

 heart, the pulsations of which are uniform with the motions of the branchial feet. 

 The motion of the feet, besides the aeration of the blood, propels (as in others of 

 this family) a strong current of water between the bases of the limbs toward the 

 mouth, bringing to it the particles on which it feeds and which it has no other 

 means of capturing. 



This interesting creature is quite rarely seen, whether from its reclusive habits 

 or actual scarcity I do not know, but it deserves the attention of students, as pre- 

 senting, both on account of its size and transparency and its somewhat anoma- 

 lous structure, one of the best opportunities of investigating these little known 

 forms. 



