422 



posable articulation. First three segments of abdomen, each 

 bearing a pair of biramous, natatory feet ; remainder of abdo- 

 men consisting of one very large trunk, supporting anteriorly a 

 pair of large, foliaceous, lobed appendages, and a pair of cylin- 

 drical false feet, and terminated posteriorly by two lamellar 

 leaping organs, and an intermediate leaf-like lobe. 



1. C. terebrans, Philippi. — Last three pairs of thoracic feet 

 with the terminal joint foliaceous. Hab. — Coast of Trieste. 



2. C. destructor, Mihi (provisional species). — All the tho- 

 racic feet, except the first two, terminated by a small hooked 

 claw. Hab. — Irish coast. 



The author, after entering into the details of the external 

 anatomy of Chelurus, maintains the necessity of considering 

 this genus as the type of a distinct family among the amphi- 

 poda, assuming as the grounds of the assigned rank the remark- 

 able condition of the posterior region of the abdomen, the first, 

 second, and third ring of this region being consolidated into 

 one great trunk, bearing three pairs of heteromorphous appen- 

 dages. Availing himself, therefore, of the characters derived 

 from these considerations, the families of amphipodous Crusta- 

 cea were analytically arranged as follows : 



'Fourth and fifth abdominal segments conflu-1 



ent ; abdominal appendages of the fourth and ( Family. 

 fifth pair very different in form (heteromor- [ Chelurid^. 

 phous). J 



f Mouth conO 

 cealed by i /-. 

 the maxii- f 



< 

 O 



P4 



fl) '■ Fourth and fifth abdominal 



segment distinct ; abdomi- lary feet. J 



nal appendages of the fourth 

 and fifth pair nearly similar 

 in form (isomorphous). 



Mouth not^ 



concealed [ xt 

 1 ,, f> Hyperion. 



by the max- 

 illary feet. 



Dr. Allman also read a paper on a new Genus and Species 

 of Entomostraca. 



The little animal which formed the subject of this commu- 

 nication inhabits the branchial sac of Ascidia communis, in 



