238 BRITISH ENTOMOSTRACA. 



Only one species has as yet been observed, which Mr. 

 Alhnan has described at length in the ' Annals and Maga- 

 zine of Natural History' for July 1847. It is found 

 swimming freely in the branchial sac of the Ascidia com- 

 munis, and has been collected in various parts of Ireland. 

 It was first publicly noticed by Mr. Paterson of Belfast, 

 who briefly mentioned it at the meeting of the British 

 Association in 1843. The species has been named by 

 Allman — 



1. NOTODELPHYS ASCIDICOLA. Tab. XXX, figs. 7, 8. 



AllmcDi, Aun. Mag. Nat. Hist., xx, 1-9, t. 1, 2, f. 1-22. 



The cephalo-thoracic segment is prolonged anteriorly 

 into a kind of beak, which is not moveable. Attached to 

 this segment we find the eye, two pairs of antennae, the 

 organs of the mouth, and one pair of natatory feet. 



The eye is situated, as in the Cyclopidse, in the centre 

 of the superior and anterior portion of this segment. It 

 is tolerably large, and is single. 



The superior antennae consist of about twelve short 

 articulations, each provided with one or more setae. The 

 inferior antennae (f. 7 a) are not branched, and are formed 

 of four joints, the last of which is in shape of a curved 

 prehensile claw. 



The labrum is well developed, and the mandibles (f. 7 b) 

 are strong organs, furnished with several stout teeth on 

 their cutting edge. 



The first pair of foot-jaws (f. 7 c) consists each of a flattened 

 peduncle and two branches ; one having six, the other 

 three articulations, and bearing several long, stout, and 

 finely plumose setae. The second pair of foot-jaws (f. 7 d) is 

 very similar to the first, but theu- two branches have fewer 

 joints ; one having three, and the other only one, but both 

 terminated by plumose setae. The third pair (f. 7 e) is 

 composed of five articulations, the basal being very large, 

 and the succeeding smaU, and furnished with stiff", not 

 plumose setae. The fourth pair (f. If) is smaller, formed 



