DESCRIPTION OF SPECIES 109 



left side. The gonad starts ventrally a little to the right of the endostyle, and curves across the posterior 

 half of the left side of the body to end rather far back in the atrial cavity. In structure the gonad is of 

 the typical Cfiemidocarpa-type, with the testis (t) occupying that part of the gonad which is attached 

 to the body wall, and the ovary (ov.) on the free or mesial side. The testis consists of long narrow 

 follicles arranged in a series along the length of the gonad. The ovary occupies the superficial part of 

 the gonad and shows oocytes of various sizes. No oviduct could be seen. Two short slender sperm 

 ducts were found along the length of the gonad, projecting from its free (ovarian) surface. 



Remarks. This is a very distinctive species not readily confused with any Cnemidocarpa yet 

 described. In the formation of the branchial sac it is most like Styela insinuosa (Sluiter), but in having 

 only three bars on each side shows a still greater simplification. A few species of Cnemidocarpa and 

 Styela have a reduced number of branchial folds. Thus in C. mortenseni (Hartmeyer) there is only 

 one on each side, and in the deep-sea species S. sericata Herdman there are no folds but twenty to 

 thirty longitudinal bars on each side. 



The presence of only one gonad in C. tricostata is also a remarkable case of simplification. 



Distribution. Antarctic (South Georgia). 



Genus Styela Fleming, 1822 

 Styela schmitti van Name f. simplex n. (Text-fig. 41) 

 Styela schmitti van Name, 1945, p. 298, text-fig. 195. 

 Diagnosis of form simplex. Characters as in the species but with about eight tentacles, a simple 

 slit-like opening of the dorsal tubercle, and only one well-developed fold and a rudimentary one on 

 each side of the branchial sac. 



Occurrence. St. 388: off Cape Horn, Tierra del Fuego, 121 m. 



External appearance (Fig. 41 A-C). The shape of the body is much as described by van Name 

 (1945) except that it is generally rather narrower and more nearly cylindrical. The sizes of the body 

 and stalk in the ' Discovery ' specimens are : 



Body length (mm.) 7 7 5 5 5 5 

 Stalk length (mm.) 433321 



A light coating of sand and broken shell covers the body of all the specimens, but does not extend to the 

 stalk. Two small projections close together at the upper end of the body mark the scarcely visible siphons. 



Internal structure (Text-fig. 41 D). The main internal characters of the form simplex are shown 

 in Table 32 along with those of van Name's type material of the species. 



Body-wall muscles 



Tentacles 

 Dorsal tubercle 



Branchial folds 



No. of stomach folds 



Anus 



Gonads 



Occurrence 



Table 32 



5. schmitti f. simplex 

 ('Discovery' material) 



External circular and internal longitudinal 



muscles forming sheets of fine strands 

 8-16; short 

 Simple transverse slit 



Well-developed dorsal fold, rudimentary 



second fold, other folds absent 

 About 20 



2 simple or slightly frilled lobes 

 2 each side ; ovaries tubular ; testes grouped 



round blind ends of ovaries 



Off Tierra del Fuego; 121 m. 



5. schmitti 

 (type material, van Name) 



Diffuse 



Probably 35-40 



Modified C-shaped slit, with open interval to 



left 

 4 folds, dorsal one highest, ventral one 



sometimes reduced 

 About 20 



A number of deep rounded lobes 

 Normally 2 each side ; ovaries elongate 



sinuous ; testes along both sides and round 



blind ends of ovaries 

 Off Montevideo, Uruguay; about 21 m. 



