2 Prof. Allman on a new genus and species of Entomostraca. 



crustacean on the coast of the north of Ireland. The latter gen- 

 tleman informs me that he procured it in great abundance in July 

 1840, while dredging off the coast of Bangor, county Down ; he 

 thinks that nine or ten Ascidice out of every twelve dredged up 

 were inhabited by the parasite, the number in each varying from 

 two to six or seven. 



In March 1846 I again obtained specimens of the little crus- 

 tacean in the branchial chamber of individuals of Ascidia com- 

 munis cast upon the shore of Dublin Bay. A careful examination 

 now convinced me that it had not yet obtained a name or place 

 in our systems, and that it was generically distinct from all 

 hitherto described forms, a fact which the more surprised me 

 when I reflected on its apparently extensive distribution, and the 

 circumstance that M. Edwards, our great authority on the Crus- 

 tacea, had made certain forms of the Ascidice the subject of 

 scarcely less elaborate and beautiful research. The following cha- 

 racters were accordingly at once drawn out, though their publi- 

 cation has been deferred up to the present time. 



NOTODELPHYS*. 



Gen. Char. Body elongated. Head scutiform and bearing in 

 front a solitary median eye. Antenna two, filiform, multiar- 

 ticulate. 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 imme- 

 diately behind the last distinct thoracic ring. Locomotive feet 

 four pairs, biramous natatory. Abdomen of about five rings, 

 the last of which is terminated by two setigerous appendages. 



Species unica, N. ascidicola. PI. I., II. 



Hab. Swimming freely in the branchial sac of Ascidia commu- 

 nis. Belfast Bay, Wm. Thompson and G. C. Hyndman, Esqrs. ; 

 Bangor, co. Down, R. Patterson, Esq.; " found in Ascidia dredged 

 from a muddy bottom at a depth of from fifteen to twenty fathoms 

 in Strangford Lough, co. Down," Wm. Thompson andG. C. Hynd- 

 man, Esqrs. ; in Ascidia dredged in Killery Bay, co. Galway, in 

 1840, R. Ball and W. Thompson, Esqrs. ; Glandore Harbour, co. 

 Cork, Dublin Bay, and Southampton water, G. J. A. 



Notodelphys ascidicola, of which I have as yet found only 

 females, measures somewhat less than a line in length and bears 

 a considerable general resemblance to Cyclops. The cephalic 

 segment is slightly prolonged anteriorly into a kind of beak, 

 immediately below which is a pair of multiarticulate setigerous 



* From v£>Tos, tergum, and 8e\<fivs, matrix. 



