35 



Remarks. The above-described form may be easily distinguished from 

 the 2 preceding ones by the comparatively much shorter and broader caudal 

 rami, and by the position of the outer-edge bristle on these rami. In the 

 living state the female of this species may moreover at once be recognised 

 by the bright bluish colour of the ova included within the incubatory pouch. 



Occurrence. Several specimens of this form have been selected from 

 material collected in different places on the south coast of Norway. Thorell 

 found it rather frequently in Ascidia venosa, and Aurivillius records it from 

 Phallusea virginea. 



Distribution. Coast of Bohusla'n (Thorell), British Isles (Brady). 



4. Notodelphys agilis, Thorell. 



(PI. XVII, 3). 

 Notodelphys agilis, Thorell, I. c. p. 40, PI. IV & V, 6. 



Specific Characters. Female. Body moderately slender, resembling in 

 shape that of N. rufescens, but of much smaller size. Incubatory pouch sub- 

 oval in outline, slightly widening distally, with the hind extremity broadly 

 rounded. Caudal rami rather slender, nearly twice as long as the anal seg- 

 ment, and somewhat narrowed in their outer part, with the outer edge finely 

 ciliated, the inner smooth; apical setae of moderate length; bristle of outer 

 edge attached to a distinct ledge in the middle of the edge. Both pairs of 

 antennae somewhat more slender than in the 3 preceding species. Last pair 

 of legs with the proximal joint rather broad and quite smooth, digitiform 

 process comparatively short; distal joint not at all constricted at the base, and 

 of a somewhat irregular form, with the outer edge angularly bent in the middle 

 and the spine of the inner edge very thin. 



Body in the living animal whitish pellucid, with the ripe ova dark fus- 

 cous in colour. 



Length of adult female scarcely exceeding 3.60 mm. 



Remarks. This form also is most readily distinguished by the shape of 

 the caudal rami, and more particularly by the exactly median position of the 

 outer-edge bristle on these rami. Otherwise it agrees closely with the 3 pre- 

 ceding species. 



Occurrence. I have met with this form in many different places on the 

 Norwegian coast, from the Christiania Fjord to Finmark (Hammerfest). It is 

 found in different kinds of Ascidians, most frequently perhaps in A. paralello- 



