igil] ASCIDIANS FROM THE COASTS OF CaNADA. 143 



short, rather close together near anterior end; when retracted they oc- 

 cupy depressions, which are surrounded by projecting ridges or collars. 

 Apertures with the usual lobes; the oral lobes occasionally have more 

 than the single tooth or process and the atrial appear to have regularly 

 4 or 5 teeth, just as in Lacaze-Duthier's genus Ctenicella. Body elong- 

 ated, laterally compressed, up to 2^ cm. in length. 



About 20 (?) bipinnate tentacles. Aperture of dorsal tubercle 

 horseshoe-shaped; opening between horns directed backwards. Dorsal 

 lamina narrow, its margin smooth. Seven folds on each side. Bars on both 

 sides of each fold, as many as 12 on a fold. Stigmata rather short, each 

 forming only about 1/8 of a circle at base of infundibulum. Infundibula 

 branched dichotomously once or twice. 



Intestinal loop narrow, horizontal. Each gonad a large oblong mass, 

 with ovary central and testicular lobes chiefly above and below ovary. 

 Oviduct directed upward from posterodorsal angle. There are as many 

 as 7 vasa deferentia projecting from the inner side of the ovary in an ir- 

 regular row. 



This species was obtained at most points where dredgings were 

 made in gravel, but never in quantity. 



It resembles C. pacifica in the structure of the gonads and pharynx 

 (7 folds, bars on both sides of folds, smooth dorsal lamina), but differs 

 from it in having the surface covered with radicoid filaments and the 

 dorsal tubercle directed backwards. From C. ocidata (Forbes) of Europe 

 it differs in having a smaller number of bars on the folds and the horns 

 of the dorsal tubercle not rolled in. 



C. retortijormis (Verrill). 



Syn. — Molgula retortifromis Verrill, Amer. J. Sc, ser. 3, vol. I, p. 56. 



This species occurs sparingly at low tide beneath rocks near the 

 station and was dredged at various points in the approaches to Passa- 

 maquoddy Bay on stony and shelly bottoms. 



It is by far the largest Caesirid occurring at St. Andrews, the majority 

 of the specimens being about 3 cm. in diameter. 



Characteristic of this form are — its thick test, long atrial siphon 

 (when extended) and the separation of the testes from the ovary. The 

 latter has the usual position — above the intestinal loop on the left and 

 above the renal organ on the right. The testes are below the renal or- 

 gan on the right side and rather extensively distributed below the ovary, 

 on the inner side of the intestinal loop on the left side. The oviduct of 

 each side is long, ending just beneath the atrial velum. The vasa de- 

 ferentia are very numerous. In one specimen 12 were counted on the 

 right side and 25 on the left. They are scattered over the inner surface 

 of the testicular mass. Their free portions are extremely short. 



