80 Miscellaneous. 



The new genus described by the author, which is founded upon 

 a specimen in the National Museum at Washington, enters into none 

 of these families. He names it 



NoTOBRANCHJEA. 



* 



Char. Bod}'^ contracted behind, presenting only a posterior 

 branchia, formed by three crests (one dorsal and two lateral), of 

 which the dorsal one alone is fringed. Anterior and posterior lobes 



Fig. 1. — Dorsal view, x4i. Fig. 2.— Ventral view, x4^. 



B, mouth ; 0, neck ; D, dorsal A, anus ; N, fin ; AP, anterior, 



branchial crest ; L, lateral PP, posterior lobes of the 



branchial crest ; T, head. foot ; \, orifice of the penis. 



of the foot long and narrow, the former free in their posterior two 

 thirds. These are also the characters of the family Notobran- 

 cha^idfc. 



The only species known to the author, which is represented by a 

 single specimen in the United States National Museum at Washing- 

 ton, is named by him Notobmnclia'ii MacDonaJdii, in honour of 

 Dr. MacDonald, who has recorded a similar arrangement of the 

 branchia in a small Gymnosome collected by him off Sydney. The 

 described specimen was obtained off Carolina in jN". lat, 3S° 10', and 

 W. long. 74° 15', by the steamer ' Albatross.' It measures 8 millim. 

 in length. 



In conclusion the author discusses the phylogenetic relations of 

 the Gymnosomata, which he regards as having originated from the 

 Aplysians, to which Dexiohrancluea ( = Pneumodennopsis, Bronn *) 

 comes nearest, being less specialized and possessing only the lateral 

 branchia. Spongiohranchcea possesses a very simple posterior bran- 

 chia, a specialization of the posterior ciliated ring which persists 

 so long in De.vlohranduva ; while Pneumoderma shows a great com- 

 plication of this posterior branchia by the presence of four crests 

 radiating from the original ring. Clionopsis shows retrogression, 

 the lateral branchia having quite disappeared and the posterior one 

 become much simplified ; and in Clione and Hahpsiiche there are 

 no traces of a special branchial apparatus. Kotohranclicm seems to 

 represent the forms from which Clione originated. — Bull. Sci. Bep. 

 du Nord, ser. 2, ann. ix. no. 6. 



* It is not very clear wliy tliis .iieueiio name is abolished in favour of 

 Dexiohranchcra, 



