ii 4 DISCOVERY REPORTS 



a compact mass of testis follicles (t) at their lower ends; this is the condition in the 'Discovery' 

 specimen from St. WS 776. Van Name (1945) is a little doubtful if these gonads are sufficiently 

 different from those of S. paessleri to justify specific distinction, but on the whole thinks that they are. 

 From a study of the 'Discovery' specimens of S. paessleri (see p. 115), and the present specimen 

 I have no hesitation in regarding these as separate species. 



There are two specimens from South Georgia (St. 123) which I include in S. magalhaensis with some 

 hesitation. Details are as follows. 



External appearance. The larger specimen (Text-fig. 43 A) is i-6 cm. high and 0-9 cm. wide, and 

 the smaller one is 1-2 by o-8 cm. The body is ovoid to conical in shape with the siphons fairly close 

 together at the upper end. Small tag-like processes are present on the lower part of the body. Else- 

 where the surface of the test is divided indistinctly into polygonal plates, each of which has a few 

 brown pigment spots (Text-fig. 43 B). 



Body wall. This is thin and semi-transparent, with weak muscles. A few finger-like endocarps 

 are scattered on the inner surface of the body wall. 



Tentacles. There are about thirty-three simple curved oral tentacles, which are quite long and 

 alternate in length. Long fine thread-like atrial tentacles are present scattered over a wide area at the 

 base of the atrial siphon. 



Dorsal tubercle. The opening of the dorsal tubercle is crescentic and faces forward. 



Branchial sac. The longitudinal bars on the four folds are arranged as follows in the larger 

 specimen: dorsal line 3 (14) 4 (12) 5 (13) 8 (11) 8 endostyle. 



Gut (Text-fig. 43 C). The oesophagus (oe.) is curved. The stomach (st .) which lies horizontally, 

 near the base of the body, is oval to diamond-shaped in outline, and has about twenty-four longi- 

 tudinal folds. Both the intestine and rectum are wide, but immediately before the anus (a.) the 

 rectum abruptly narrows. About twelve reflected lobes subdivide the margin of the anus. 



Gonads (Text-fig. 43 D-F). Both specimens have two gonads on each side. The ovaries (ov.) vary 

 from rather short and straight to quite long and sinuous. At the lower end of each ovary are two, three, 

 or four rounded masses of testis follicles (t.), lying at some distance from the ovary. 



Remarks. Although I have provisionally included these two specimens in S. magalhaensis, the 

 pigmentation and sculpturing of the test, and the failure of the testicular masses to coalesce, are 

 differences which might indicate some systematic distinction. But at present there is too little 

 material, and the similarities to typical specimens of S. magalhaensis are too great, to permit separating 

 those two specimens from that species. 



A number of other species have been described from the southern part of the South American coast, 

 which are sufficiently like S. magalhaensis to raise some doubts regarding their validity. The characters 

 of these species are shown in Table 33 for comparison with the present species. 



Conclusions regarding the validity of Herdman's three species must be cautious, as the descriptions 

 are not sufficiently detailed. It does seem, however, that S. oblonga differs sufficiently from S. magal- 

 haensis to avoid confusion. As nothing is known regarding the gonads or gut of S. flava, the species 

 must remain of uncertain value. 5. glans appears to be very like 5. magalhaensis, especially in the 

 structure of its gonads. Here again details of the gut are wanting, but S. glans might well prove to be 

 a synonym of S. magalhaensis. Van Name (1945) has argued that S. melincae is identical with S. magal- 

 haensis, and the above comparison shows the similarities on which his conclusion rests. Only the 

 numbers of tentacles and of branchial bars on the folds differ markedly and these are both characters 

 varying with body size ; Michaelsen's specimens were larger than Arnback's specimens. 



Distribution. Subantarctic (southern part of Argentine coast; Magellan region; PGuaitecas 

 Islands, Chile); Antarctic (MacRobertson Land, South Georgia). 



