94 PROFESSOR W. A. HERDMAN ON THE 



thin, leathery, raised at intervals to form little pointed tubercles, the larger of which 

 are echinatecl (fig. 5). Mantle muscular, with regular circular and longitudinal bands. 

 Branchial Sac with four large folds on each side. There are six to nine bars on a fold, 

 and four in the interspace. Dorsal lamina a broad plain membrane. There are about 

 thirty very long simple tentacles and some intermediate smaller ones. The dorsal 

 tubercle has both horns coiled inwards to form short spirals (fig. 8). There are two or 

 three long gonads on each side, and many endocarps. Fig. 7 shows the arrangement 

 of the alimentary canal. 



In the smaller, more globular specimens the conical spiny tubercles on the test are 

 relatively more numerous and more closely and regularly placed (see figs. 2, 3, 4, and 6). 

 The Challenger specimen figured, from Kerguelen, was intermediate in size to the 

 larger and the smaller Scotia examples, and was smoother in character of test. 



Styela paessleri, Michaeisen. (Plate, figs. 12 to 14.) 



This species was described by MICHAELSEN in 1900 from specimens obtained in the 

 Straits of Magellan. The Scotia specimens from the Falkland Islands seem to be 

 rather larger on the whole, but agree in essential characters. 



The following description, from the Scotia material, may be useful : There are 

 about twenty specimens, varying in size from 1 cm. to 3 cm. in length by 1'5 cm. in 

 average breadth, obtained from Station 118, at the Falklands, depth 6 fathoms; and a 

 couple from Port Stanley, February 2, 1904, 6 fathoms. 



The colour varies from a creamy white to a yellowish brown, and the surface of the 

 test is in most places closely wrinkled. The branchial sac has four folds on each side, 

 the largest being those adjacent to the dorsal lamina, with ten bars each, while the others 

 have usually six bars. Fig. 12 gives the plan of both sides of the branchial sac as seen 

 in section, with the number of bars and of rows of stigmata shown by the figures. The 

 folds have from five to ten bars, and there are from two to five (usually four) bars in the 

 spaces between. These numbers agree fairly well with those given by MICHAELSEN. 

 The transverse vessels are of three sizes arranged with regularity : 1 3 2 3 1, and 

 having a narrow horizontal membrane in addition crossing the meshes (fig. 13). Most 

 of the meshes are square, with five to seven stigmata in each. The extreme dorsal and 

 ventral meshes are more elongated transversely, and contain a greater number of stigmata. 



The dorsal tubercle is of curious form (fig. 14), a simple crescent with the horns 

 anterior and having a globular excrescence in the concavity. The dorsal lamina is a 

 plain membrane. The tentacles are crowded and number about a hundred. They are 

 of two sizes, roughly fifty of each. MICHAELSEN records only sixty tentacles, but as 

 the specimens he examined were smaller than ours, the difference need not be regarded 

 as important. 



Although some of the above characters do not agree precisely with those given by 

 MICHAELSEN, still the differences are not, I think, greater than what may reasonably be 



(ROY. soc. EDIN. TRANS., VOL. XLVIII., 312.) 



