DESCRIPTION OF SPECIES in 



by: (i) the smaller number of tentacles; (2) the simpler dorsal tubercle; and (3) the greater reduction 

 of the branchial folds. 



The similarities between the 'Discovery' specimens and those described by van Name are too 

 great to justify specific distinction. The degree of distinctness is best indicated, I believe, by a separate 

 form, f. simplex, the name referring to the tendency towards simplification in several organs. 



Distribution. Off Uruguay (typical form) ; off Cape Horn, Tierra del Fuego (f. simplex). 



Styela insinuosa (Sluiter) (Text-fig. 42) 

 Tethyum insinuosum Sluiter, 1912, p. 24, pi. 2, figs. 28-32; pi. 3, figs. 33-35; pi. 4, fig. 44. 

 Occurrence. St. 156: S. Georgia, 200-236 m. St. 474: S. Georgia, 199 m. 



External appearance (Text-fig. 42 A). The specimens are all more or less cylindrical, with the 

 siphons fairly close together at the upper end. The whole surface is covered with low wart-like 

 swellings, and the colour in the preserved state is brown. The largest specimen is 5-3 cm. high by 

 2-0 cm. wide, and the smallest is 2-2 cm. by 1-5 cm. 



2.0 cm 



Text-fig. 42. Styela insinuosa (Sluiter) (St. 474): A, external appearance; B, gut; C, left gonad. 



Body wall. The body wall is quite thick, owing to the existence of powerful muscles which 

 constitute an inner longitudinal, a middle circular, and an outer longitudinal layer. 



Tentacles. There are twenty-four oral tentacles in the largest animal and about sixteen in the 

 smallest; Sluiter (1914) found up to thirty-two. The atrial tentacles are numerous and stand in a single 

 circle on the margin of a low velum within the atrial siphon. 



Dorsal tubercle. The slit of the dorsal tubercle is C-shaped with inrolled horns, the open interval 

 facing forward. 



