ARTICULATA. 109 



American species. Tlie name of the latter is changed from reticulata^ as 

 this has been ah'eady applied to a European species. 



Fam. 4, ApodidcB. This family includes Latroille's fifth order, PJiyllo- 

 2)oda, in which the body is either naked, inclosed in a bivalve shell, or with 

 the head and thorax covered with a carapace. The b<;)dy is divided into a 

 great nui^.bor of segments, most of which have foliaceons feet adapted for 

 breathing, the number of which varies from eleven to sixty pair. Antennae 

 two or four in number, and not adapted for swimming; eyes two or 

 three. 



A2ms {pi. 78, jig. 25) has a large carapace covering nearly the entire 

 body ; one pair of short antennfe, and sixty pair of branchial feet. Schieffer 

 enumerated the number of pieces which enter into the composition of the 

 body, and found them to amount to 1,802.601, He found that each of the 

 caudal filaments in Ajxts cancrifonnis contains 480 articulations. It 

 inhabits fresh water ponds, and swims equally well with the back above or 

 below. It reappears in desiccated ponds in two daj'S after a rain ; and it 

 has been found in ponds that have been without water for several years, 

 whence it may be inferi-ed that the eggs retain their vitality for a long time. 

 They feed upon the niicroscopic Entomostraca, and are in turn devoured 

 by frogs. 



The metamorphosis of Ajnis is much like that of Cyclops, Lern:iea, etc. 

 When the young leave the ^gg., the body is narrowed posteriorly, the tail is 

 wanting, the antennae are large, and the first and only pair of feet are 

 robust, and longer than the body, thus j^resenting opposite characteristics 

 from the adult. The length of the common European species, A. cancri- 

 fonms^ is two and a half, and the breadth one and a half inches. There 

 are but few species known. One has been described from the West Indies, 

 one from the eastern side of the Rocky Mountains, and another from the 

 Sandwich Islands. 



Branchipus jyisciformis {pi. 1^.,fig. 26) was described under this name, 

 according to W. Baird, by Schteffer, in 1752, and was subsequently named 

 Chirocephalus diaphanus.^ by Prevost. It has two pedunculated eyes, four 

 antennsB, eleven pairs of branchial feet, and there is no shield. In the male, 

 the larger pair of antennse are j^rehensile, resembling mandibles, their base 

 is large and fleshy, and the outer joint curved and cylindrical. From the 

 base of these antennre arises a pair of large flexible proboscidiform organs 

 with their appendages, all of which are usually rolled up beneath the head. 

 In the female the large antenna3 have a singular structure, being short, 

 compressed, bent downwards, pointed at the end, and unprovided with 

 appendages. The species figured is more than an inch long, and is found in 

 pools swimming upon its back. As in nearly all the Entomostraca, the 

 branchial feet are kept moving continually. These animals swim with the 

 aid of the tail, darting through the water like small fishes. They feed upon 

 dead animal and vegetable matter. The female has an external branchial 

 sac, and the young undergo a metamorphosis. 



Limnadia is inclosed in a bivalve shell somewhat as in Cypris, but the 

 animal is larger, being nearly half an inch long. The ximerican species, 



313 



