3907] Kilter. California Coast Ascidians. 35 



any single one of the other characters above mentioned. It can 

 hardly be regarded as weighty enough, though, to offset all the 

 others. 



The two particulars which, in connection with those that tend 

 to break down the distinction between Ascidia and Ascidiclla, 

 will probably entitle the form to independent generic rank, are 

 the broad muscular velum, or valve, that carries the tentacles; 

 and the great external transverse vessels, or pipes, of the 

 branchial sac. 



Even in the genera like Cijntlna and Microcosmus, where the 

 "Tentakeltrager" reaches its greatest development, I know of 

 no other instance of its having a width and strength at all com- 

 parable with what we have here. Not only is it distinctly broader 

 than the tentacles are long, but it is well provided with muscle 

 fibers. 



Although the large transverse vessels are not so unique as 

 the tentacle carrier, corresponding as they undoubtedly do to 

 the "vessels of the first order" in numerous other Ascidians, 

 there appears to be no instance in which they are so large rela- 

 tively to the other transverse vessels, and particularly where their 

 position is so largely on the external surface of the branchial 

 membrane. 



In the wide, simple intestinal loop this species resembles A. 

 arcliaia, Sluiter, but this is about the only character common to 

 the two. Relative to the Ascidiella character of the renal organ, 

 it may be recalled that Kiaer ( '93 and '96) has pointed out that 

 the disposition of these organs cannot be relied upon altogether 

 for separating the two genera, since in Ascidiella obliqua of the 

 Norwegian seas, they are restricted to the intestinal wall. Kaier 

 consequently excludes this point from his definition of Ascidiella. 

 One specimen was taken at station 4405, near San Clemente Isl- 

 and, 654-704 fathoms, April 9, 1905 ; and seven from station 4425 

 (see data under Ciona mollis). 



Ciona mollis, n. sp. 



PI. 3, figs. 35 to 38. 



External Characters. Very soft and flabby, preserved speci- 

 mens all in a collapsed and more or less shriveled condition. 

 Form variable, usually somewhat longer than broad, but never 



