igil] ASCIDIANS FROM THE COASTS OF CANADA. 141 



animal is sand-covered, these are present over the entire surface, in- 

 cluding that of siphons. If not sand-covered, the free surface has numer- 

 ous minute adhesive tubercles. 



From 15 to 25 tentacles, pinnate or slightly bipinnate. Aperture 

 of dorsal tubercle varying from a simple slit to the shape of an imperfect 

 S, which Hartmeyer suggests is characteristic of the genus Ctenicella. 

 Dorsal lamina with tapering distant teeth. Seven folds on each side of 

 pharynx. Bars on both sides of each fold, as many as 4 (or occasionally 5) 

 on a fold. Stigmata in infundibula (divided once), each stigma usually 

 representing ^ of a circle and simulating the longitudinal stigmata of 

 other groups. 



Intestinal loop narrow, more or less bent. Anus with smooth mar- 

 gin. Gonads some distance above intestinal loop and renal organ re- 

 spectively. Ovary short, bent with the concavity ventral; oviduct 

 passing from its anteroventral angle; testicular lobes along the upper side 

 of the posterior end of the ovary or in a semicircle around its posterior 

 end; the single vas deferens projects from the centre of the inner side of 

 the ovary. 



The species to which this form is most nearly related, and the re- 

 spects in which it differs from them are as follows : — 



Molgida complanata Aid. & Hanc. — 7 folds on left side instead of 6, 

 smaller number of bars and larger infundibula with the stigmata in trans- 

 verse rows. 



Ctenicella lanceplaini Lac.-Duth. — more teeth on each atrial lobe, 

 deeper infundibula, more regular transverse rows of stigmata, a larger 

 number of bars. 



C. morgatae Lac.-Duth. — the smaller number of bars, the toothing 

 of the posterior ends of the folds and the position of the testicular lobes. 



At first I referred this species to Verrill's Molgula littoralis, but 

 Dr. Van Name has informed me by letter that the latter (from his pre- 

 liminary study of Verrill's specimens) has the long bent oviduct of the 

 next species. He also states that he has not yet found any CteniceUce 

 among his material. He suggests that it is something new to the region. 

 There is the probability that it has been introduced from Europe since the 

 time that Verrill collected in the Bay of Fundy region. Its derivation 

 from C. tenax (Traust.), a nearly related Arctic form (occurring in Green- 

 land) with usually only 6 folds, and its subsequent extension down the 

 coast is another possibility. It is possible that further study will make 

 it necessary to unite this species with the three from Europe into a single 

 species, 



Hartmeyer has retained Lacaze-Duthier's Ctenicella with an alter- 

 ation of the diagnosis. His group does not seem to be a more natural 



