106 DISCOVERY REPORTS 



diameter about 0-4 cm. possess a small caecum (Text-fig. 38 A, p.c), but all specimens over about 

 2-0 cm. in diameter lack a caecum (Text-fig. 38 B). There are about twenty-four folds on the wall of 

 the stomach, but they are internal and are visible from the outside only in small specimens (see 

 Text-fig. 38 A, B). 



Biology. Text-fig. 39 shows the size-distribution, in different months, of the specimens from two 

 collecting areas: (1) the Falkland Islands and Patagonian Shelf; and (2) South Georgia, the South 

 Shetland Islands, the South Sandwich Islands and Graham Land. In both populations breeding had 

 probably started before March, as indicated by the presence of young individuals in that month. In 

 the more southerly localities no very young specimens were taken in April, but it must be pointed out 

 that the total numbers collected at this time were very small. The samples from the Falkland Islands 

 and Patagonian Shelf, taken in May, include quite a high proportion of young individuals, suggesting 

 a breeding season extending farther into the southern autumn in the Subantarctic population, than 

 in the Antarctic population. 



The histograms for March (Antarctic) and May (Subantarctic) point to the presence of at least two 

 year-classes, and the animals may possibly live for two years or more. These are only very tentative 

 suggestions, however, as the numbers of specimens are small and the months of collection limited. 



Distribution. Subantarctic (Falkland Islands, Patagonian Shelf, Kerguelen) ; Antarctic (Graham 

 Land, Kaiser Wilhelm II Land, South Georgia, South Shetland Islands, South Sandwich Islands, 

 Enderby Land, Queen Mary Land, MacRobertson Land). 



Cnemidocarpa tricostata sp.n. (Text-fig. 40) 



Diagnosis of species. Ventral half of body with a thick coat of test hairs, dorsal half without hairs. 

 About twenty-two oral tentacles, and a single circle of atrial tentacles. Dorsal tubercle with a straight 

 opening. Branchial sac without folds, but with three longitudinal bars on each side. Stomach with 

 about thirteen folds. One gonad on the left side and none on the right. 



Occurrence. St. 27: S. Georgia, nom. 



External appearance (Text-fig. 40 A). The single specimen is 1-2 cm. high and 0-9 cm. across at 

 the widest point. In the preserved state it is pear-shaped with a swollen base which apparently 

 rested on a soft substratum. The upper part of the body narrows towards the siphons which are close 

 together and project as short tubular papillae with 4-cleft openings. The test on the upper half of the 

 body is broken up into rounded wart-like swellings, which in some places have the appearance of 

 being arranged in circles passing round the body. No test hairs or foreign particles are present on the 

 upper part of the body, which is yellowish grey in colour. The lower half bears a thick coat of test 

 hairs to which a few sand grains adhere. These hairs are unbranched and not very long. They arise 

 either singly or in groups of two or three. 



Test. The test is rather thin but tough. 



Body wall. The muscles of the body wall are arranged in two layers, an external one of weak 

 circular muscles and an internal one of strong longitudinal muscles. A few large clear endocarps are 

 attached to the inner surface of the body wall. 



Tentacles. There are about twenty-two simple oral tentacles and a single circle of many slender 

 atrial tentacles. 



Dorsal tubercle. The dorsal tubercle is rather small, with a simple oval transverse opening 

 (Text-fig. 40 D). 



Branchial sac. There are no folds on the branchial walls, each side having only three tall longi- 

 tudinal bars (Text-fig. 40 C, Lb.). The meshes are therefore long, and each accommodates up to thirty 

 stigmata (Text-fig. 40 E). Slender parastigmatic transverse bars pass across the centres of the rows 



