50 



dorsally almost semicircular in outline ; rostral prominence terminating in a 

 knob-like point. The 3 succeeding segments gradually increasing in size, with 

 the lateral parts not extant. Incubatory pouch subquadrangular in shape and 

 scarcely dilated behind, with the extremity transversely truncated and slightly 

 overlapping the base of the tail. The latter about half the length of the 

 anterior division, with the last segment considerably larger than the preceding 

 one and not dilated distally. Caudal rami comparatively short, scarcely exceeding 

 half the length of the anal segment, and terminating in a blunt point. Eye 

 apparently absent. Anterior antennae scarcely attaining half the length of the 

 head, and composed of 8 joints, the 3 or 4 proximal ones lamellarly expanded, 

 the 4 outer joints abruptly much narrower. Posterior antennae with the middle 

 joint somewhat dilated; apical claw well developed and accompanied by 2 

 very small bristles. Endopodal part of maxillae with 3 setae inside the base, 

 terminal joint somewhat fusiform in shape and edged with 6 setae, 2 of which 

 issue from the strongly convex inner edge, the 4 others from the tip. Anterior 

 maxillipeds with the claw-like spine issuing from the 2nd basal joint very strong, 

 terminal part short, biarticulate. Posterior maxillipeds with the middle joint 

 quite unarmed, terminal joint carrying 3 subequal setae. The 4 anterior pairs 

 of legs somewhat diminishing in size behind, and wanting the usual plumose 

 seta inside the 1st basal segment; outer ramus in all the pairs larger than the 

 inner and armed outside with strong spines. Last pair of legs with the proximal 

 joint rather broad at the base and provided at the end outside with the usual 

 small bristle; distal joint scale-like, with the outer edge boldly curved, tip 

 provided with a single small bristle. 



Male resembling in shape the males of most other Doropygidae, being 

 however easily recognisable by the large size of the head. 



Body in the living animal of an uniform whitish colour. 



Length of adult female 2.10 mm., of male 1.50 mm. 



Remarks. The present form may be easily recognised from the other 

 known Doropygidae by its short and clumsy body, and more particularly by the 

 unusual development of the head and the characteristic shape of the incu- 

 batory pouch. 



Occurrence. I have taken this form not unfrequently in several places, 

 both of the south and west coasts of Norway, it is generally found within 

 the branchial cavity olPhallusia obliqua, more rarely in that of other kinds of 

 Ascidians. The animal is very slow in its movements, and is quite unable to 

 move freely in the water. 



Distribution. Coast of Bohuslan (Aurivillius). 



