54 



tennae somewhat shorter than the head, and composed of 9 well defined joints, 

 the first 2 of which, as usual, are the largest, though combined not much 

 longer than the remaining part of the antenna. Posterior antennae rather stout, 

 with the terminal joint much shorter than the middle one; apical claw very 

 strong. Mandibular palp with the outer ramus very short and broad, undivided. 

 Endopodal part of maxillae with 4 setae inside the base, one of them much 

 larger than the others; terminal joint fringed inside with 4 small setae and 

 carrying on the slightly exerted tip 3 somewhat longer setae. Anterior maxi- 

 lipeds with the terminal part rather slender, 3-articulate, middle joint consider- 

 ably longer than the others. Posterior rnaxillipeds distinctly 3-articulate, with 

 the last joint simple, fringed with 4 setae. 1st pair of legs with the rami not 

 much different in length, but rather unlike in structure, the inner ones being, 

 as in the 3 succeeding pairs, only composed of 2 joints, the distal one much 

 the larger and clothed with unusually long and slender setae. Outer ramus 

 of the 3 succeeding pairs longer than the inner and tapered distally, with 

 the 1st joint very large, setae much reduced, being wholly absent in the 4th 

 pair. Last pair of legs with the distal joint narrow linear in form and pro- 

 vided on both edges with small spinules. 



Male much smaller than female and without any traces of dorsal expansions. 



Body of female, in the living state, of a pale yellowish brown hue, with 

 the ripe ova fuscous green. 



Length of adult female attaining 4.20 mm.; that of male scarcely exceeding 

 1.40 mm. 



Remarks. This form was described in the year 1859 by Thorell and 

 referred by him to the genus Doropygus. In a note to his description he has 

 however alluded to its apparent relationship to the genus Notopterophorns of 

 Costa. Indeed, it ought evidently to be referred to that genus, though the 

 dorsal expansions of the body are far less conspicuous than in the other 

 known species. 



Occurrence. The present form is not seldom found in large Ascidians of 

 different kinds. I have noted it from many places on the Norwegian coast, 

 from the Christiania Fjord at least to the Trondhjem Fjord. Like most other 

 Doropygidae, it is very slow in its movements. 



Distribution. Coast of Bohuslan (Thorell), British Isles (Norman & Scott). 



