I3 2 DISCOVERY REPORTS 



Branchial sac. On each side of the branchial sac are six folds, with the following arrangement of 

 longitudinal bars as seen in a moderate sized animal: dorsal line o (5) o (6) o (8) o (7) o (6) o (5) o 

 endostyle. Van Name (1945) wrongly quotes Hartmeyer (1914) as giving the number of bars on the 

 folds as from two to four, whereas Hartmeyer in describing the type specimen stated that there were 

 from two to four bars on one side of the folds. The total number would thus correspond to the number 

 found in the ' Discovery ' specimens. 



Gut. The shape of the gut seems to be characteristic and affords the best means of distinguishing 

 between this species and M. manhattensis (De Kay). In M. platei the primary loop is closed for most 

 of its extent, as it is in the other species, but the secondary loop also is almost completely closed. 

 About half of the intestinal loop is bent at a sharp angle to lie almost horizontally over its lower half 

 (see Text-fig. 56 A), bringing the bend of the primary loop in contact with the rectum. In M. man- 

 hattensis the curvature of the secondary loop is typically the arc of a circle with the opening of the loop 

 dorsal, contrasted with the flattened horizontal secondary loop with the opening posterior, in M. platei. 



Gonads. The left gonad lies in the secondary intestinal loop and the right gonad lies obliquely above 

 the renal sac. (Text-fig. 56 A). The central ovary (ov.) and fringing testis (t) are much as described 

 by Hartmeyer. The oviduct (od.) is terminal and the sperm duct (s.d.) a short distance from it. 



Remarks. This species has previously been known only by a single specimen from the coastal waters 

 of Chile near Chiloe Island. Van Name (1945), while allowing the species to stand, was in some doubt 

 whether it differed sufficiently from M. manhattensis to justify separation, but the plentiful material 

 of the 'Discovery' collection confirms Hartmeyer's view that the two species are distinct. 



Distribution. Coastal waters of Chile (about 38 S. to 44 S.). 



Molgula malvinensis Arnback (Text-fig. 57) 

 Molgula malvinensis Arnback, 1938, p. 5, pi. 1, figs. 1-3; text-fig. 1. 



Occurrence. St. 159: S. Georgia, 160 m. St. 474: S. Georgia, 199 m. 



External appearance. The largest specimen measures 4-3 cm. long (antero-posteriorly) by 3-0 cm. 

 high (dorso-ventrally) by 2-0 cm. wide and is considerably larger than specimens hitherto obtained ; 

 the smallest is 2-7 by 1-7 by 1-5 cm. The body is almost completely hidden by adhering sand and 

 small stones, the contracted siphons alone being visible on the upper surface. Arnback (1938) 

 states that the test bears irregular hair-like processes. The test processes of the specimens in the 

 ' Discovery ' collection are either grouped together in small bunches or are compound, several hairs 

 arising from a short common stem. At their outer ends these hairs are usually expanded, where they 

 are attached to the small stones covering the body. 



Tentacles (Text-fig. 57 B). The tentacles differ somewhat from those illustrated by Arnback 

 (1938, text-fig. 1) who shows them as bi-pinnate. Van Name (1945) states that the tentacles are like 

 those of M. occidentalis Traustedt, which are at least tri-pinnate. In the ' Discovery ' specimens there 

 are about eight large tentacles and the same number of very small ones. Even the large tentacles are 

 only once pinnate and the branches, which number four or five on each side, are very short. 



Dorsal tubercle (Text-fig. 57 C). The dorsal tubercle has a C-shaped slit with the horns inrolled; 

 the opening of the C faces right in one of the specimens examined and left in the other. 



Branchial sac. There are, as reported by Arnback, seven folds on the right side of the branchial 

 sac and six on the left side. Longitudinal bars are distributed as follows in the largest specimen: 



Left — dorsal line 1 (18) 1 (22) 1 (21) 2 (20) 2 (20) 1 (14) o endostyle. 



Right — dorsal line 2 (14) 1 (21) 1 (26) 1 (22) 1 (22) 1 (20) 1 (16) o endostyle. 



In this specimen there are twice as many bars on the folds as in Arnback's specimens, a fact cor- 

 responding to the greater body size. In the type specimen the edge of the dorsal lamina was toothed, 





