474 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 45. 



species pending the time when dissections of a sufficiently large 

 number can be made to test more thoroughly the question of corre- 

 lation of the variations. 



In the structure and disposition of the furriness of the test 

 S. Ttemicsespitosa is, so far as I can determine, unique in the genus, 

 it resembling more closely in this respect the Polycarpa, or Pandocea 

 fihrillata of Alder and Hancock than any other ascidian. 



The species considerably resembles, particularly in some of its 

 variations, S. milleri Ritter and S. sigma Hartmeyer. From milleri 

 it differs, not only in the extent and arrangement of the test fur, but 

 in the smaller number of branchial tentacles, the smaller number of 

 vessels on the branchial folds, and the smaller number of testis lobes. 

 And S. sigma appears to be wholly devoid of the test fur, to be a much 

 larger species, and to possess a greater number of vessels between the 

 folds of the branchial sac. Furthermore, the gonads of sigma, seem- 

 ingly two on each side in all cases, are, as I infer from Hartmeyer's 

 description, hermaphroditic, and so lacking the separate testicular 

 masses characteristic of hemicsespitosa. Hartmeyer does not men- 

 tion the point in his text, but his figure shows only the two pairs 

 of cylindrical bodies on each side; and in several other species which 

 he says are rather similar to sigma the gonads are expressly stated to 

 be hermaphroditic. But the species with which hemicsespitosa 

 undoubtedly has most in common is S. loveni (Sars), some individuals 

 of this species presenting an approach to the hairiness of the test so 

 conspicuous in S. liemicxspitosa. And interestingly enough loveni 

 runs through a range of shape variations, as shown by Hartmeyer and 

 others, almost exactly parallel with that presented by our species. 

 But the test hairiness is almost wholly wanting in most specimens of 

 loveni. This difference between the two species may be correlated 

 with their difference in habitat, Jiemicsespitosa being a dweller on 

 muddy bottoms, while loveni is usually found closely adherent to 

 stones, shells, etc. The two species seem to be well differentiated, 

 too, in the character of the branchial sac, the folds in loveni being 

 less prominent, and the whole membrane, both folds and interspaces, 

 carrying fewer longitudinal vessels. 



The distribution of the species is surprising. All the specimens 

 except two are from the coast of southern and Lower California, and 

 from depths not exceeding 61 fathoms. Two individuals are from 

 Bering Sea, taken at a depth of 225 fathoms. The agreement between 

 the northern and southern specimens is very close, the only difference, 

 so far as I am able to sea about which there may be a question, 

 being in the testis lobes. These are somewhat more numerous and 

 voluminous in the Alaskans. 



Albatross 2838, lat. 28° 12' N.; long. 115° 09' W., off Lower Cali- 

 fornia, 44 fathoms, bottom gn. m.. May 5, 1888; about 20 specimens, 

 all pyramidal form. 



