THE PELAGIC TUNICATA. 205 



There is only one specimen of this peculiar form in the collection. It 

 was taken with the trawl, which had been down 830 fathoms, at Station 25 

 A. A. (in the vicinity of the Marquesas Islands) on Sept. 14, 1899, Lat. S. 

 8° 48', Long. W. 139' 48'. Surface temp. 80\ Bottom temp. 38\ 



It seems probable that, like P. sjiinosmn, to which it is most nearly 

 related, it is a deep-sea form. It resembles F. spinosum in the character of 

 the spines covering the test and possibly in the character of the test itself, ' 

 though descriptions of this structure in this latter species are meagre. It 

 also resembles it in the arrangement of muscles about the branchial orifice 

 and in the course taken by the peripharyngeal band. It differs in size, in the 

 possession of an atrial tentacle, and probably in the shape of the zooid and 

 in the character of the digestive tract. 



It will probably appear to students of the pelagic Tunicata that the 

 species here described is sufficiently distinct from any hitherto known 

 Pyrosoma to deserve being regarded as the type of a new genus. This was 

 the view held by us until a considerable collection of Pyrosomae recently 

 came into our hands through the kindness of Professor C. H. Gilbert of the 

 Leland Stanford Junior University, that was secured by the " Albatross " 

 on her Hawaiian cruise during the summer of 1902. In this collection are 

 several specimens identical with the colony here described, excepting that in 

 some of them the four processes about the cloacal orifice are absent. We 

 had regarded these as the most important characteristic of the new genus 

 which it was our intention to establish. We consequently decided to adopt 

 the more conservative course and, for the present at least, treat the new 

 form as a highly distinct species of the old genus. 



