423 
which it may be observed swimming freely during, perhaps, all 
seasons of the year. ‘The author describes it under the name 
of Notodelphys ascidicola, and assigns to it the following ge- 
neric characters : 
Noropetpuys,* Mihi. 
Gen. Cha.—Body elongated ; head scutiform, and bearing 
in front a solitary median eye; antenne two, filiform, multi- 
articulate ; mouth with a pair of mandibles, and surrounded 
by five additional pairs of appendages, of which the anterior, 
as well as the last two pairs, are prehensile ; thorax having 
but two rings distinct, the anterior one being confounded with 
the head. Female with a large dorsal ovigerous receptacle 
immediately behind the last distinct thoracic ring. Locomo- 
tive feet, four pairs; biramous natatory, each pair having an 
intermediate plate ; abdomen with about five rings, the last of 
which is terminated by two setigerous appendages. 
Species unica.—WN. ascidicola. Hab.—swimming freely 
in the branchial sac of Ascidia communis, Irish and English 
coasts. 
The author, after entering into numerous details relative to 
the anatomy of the new entomostracon, and describing four 
distinct phases in its development, maintained that the ovige- 
rous receptacle was formed by a peculiar development of the 
dorsal arches of a certain number of posterior thoracic rings, 
and that it was the true representative of the singular, elytroid, 
dorsal appendages of the thorax in Anthosoma, Cecrops, and cer- 
tain other suctorial crustacea. He was, moreover, of opinion, 
that the genus Notodelphys presents us with a most interesting 
transitional form between the true entomostraca and the suc- 
torial crustacea. Its perfect mandibulate mouth will at once 
place it with the former,—a position, indeed, which its highly 
developed natatory feet and active habits, as well as its general 
* From verog, tergum, and dedpi¢, matrix, 
