70 



Gen. 13. Pteropygus, G. O. Sars, n. 



Generic Characters, Body (of female) perfectly segmented, with the an- 

 terior division well marked off from the posterior, but less tumid than in 

 Botryllophilus. Tail much narrower than the anterior division, and only com- 

 posed of 3 segments; caudal rami short, clawed at the end. Antennae and 

 oral parts of a structure similar to that in Botryllophilus. The 4 anterior pairs 

 of legs with both rami short, uniarticulate, the outer one spiniferous, the inner 

 setiferous. Last pair of legs transformed to 2 large wing-like lamellae encom- 

 passing the last trunkal segment and meeting each other at the base dorsally, 

 partly obtecting the single cake-like ovisac. 



Remarks. The present new genus is nearly allied to Botryllophilus, but 

 differs conspicuously in the perfect segmentation of the anterior division of 

 the body, the 3-articulate tail, and more particularly in the very unlike appear- 

 ance of the last pair of legs, which are developed in a somewhat similar 

 manner to that in the genus Ascidicola. The genus comprises as yet only a 

 single species, to be described below. 



23. Pteropygus vestitus, G. O. Sars, n. sp. 



(PI. XXXIII). 



Specific Characters. Female. Body comparatively short and stout, with 

 the anterior division of nearly equal width throughout, and only very slightly 

 vaulted dorsally. Cephalic segment scarcely narrower than the succeeding 

 segment and evenly rounded in front, rostral prominence very slight. Last 

 trunkal segment well defined and abruptly narrowed behind. Tail about 

 equalling in length the trunk, and narrow cylindrical in form, with its 3 seg- 

 ments of nearly equal size. Caudal rami turned straight outwards, and armed 

 at the end with 4 strong curved claws arranged in pairs. Eye very small. 

 Anterior antennae short and compressed, broad at the base, but rapidly tapered 

 distally, being composed of 6 well defined joints clothed in front with numerous 

 unequal rigid setae. Posterior antennae very like those in Botryllophilus, last 

 joint armed with 8 spines, 4 on the outer edge and 4 on the tip. Mandibles 

 with the 2 outermost teeth of the cutting edge much larger than the others; 

 palp very large, nearly twice the length of the body of the mandible, and of 

 a structure very similar to that in Botryllophilus. Maxillae likewise rather 

 similar, though having the terminal joint of the palp distinctly defined at the 

 base. Anterior maxillipeds comparatively more fully developed than in that 



