222 MKIT1SH I.NTOMOSTRACA. 



(lie upper edge of the centre plate. The second pair 

 (f. 2 c) is flat and stout, composed each of a body which is 

 indistinctly divided into three segments. The anterior 

 edge is prominently marked \vitli several eminences, 

 from each of which spring two rather long setae, directed 

 towards the month. The posterior or third pair of foot- 

 jaws (f. 2/) is much larger than the preceding, and is 

 formed of seven rings, the first two of which are large in 

 proportion to the other live. 



The legs are five pairs in number, and the first four, as 

 in the Cyclopidie, are double. The basal portion consists 

 of two articulations. In the first pair (f. 2y) the external 

 branch consists of three joints, and the internal of two. 

 In the three succeeding pairs (f. 2 //) each of the branches 

 is composed of three segments, and all are furnished with 

 plumose seta?. The fifth pair is differently formed from 

 the others, and is strong and well-developed compared 

 with that of the Cydopidse. They differ also from 

 each other in the two sexes. Those of the male (f. 2 i) 

 are almost cylindrical, and consist of two unequal branches 

 arising from a common footstalk. The right branch is 

 much the larger of the two, and is formed of three articu- 

 lations, the last of which is terminated by a long and 

 strong hook. The left has four rings, and is terminated 

 by two short spines. This pair of legs is erroneously con- 

 sidered by Jurine to be the sexual organs; the shorter of 

 the two branches containing, he believes, the organ itself. 

 In the female (f. 2 /') the right branch is very much the 

 larger of the t\vo, and consists of three joints, the last of 

 which is terminated by a strong curved claw. The left 

 branch is very slender, composed of only one joint, and a 

 terminal spine. These organs in the female arc called. 

 by Jurine, the "fulcra, or supports of the external ovary." 



The dorsal vessel, or heart, is verv distinctly to be seen 

 under the second and third segment of the body. It is 

 oval, and gi\es origin to two vessels of equal si/e, one 

 going to the head, and the other to the abdomen, and has 

 another organ attached to it, which is called by Jurine 



