1907] Hitter. California Coast Ascidians. 13 



species, but fr,om this it differs in the absence of the spirally 

 inrolled horns of the hypophysis mouth: in the less number of 

 tentacles, owstoni having thirty; and in the larger number of lon- 

 gitudinal vessels on the branchial folds, owstoni having seventeen 

 or eighteen of these. 



As our information now stands, the distribution of these Cyn- 

 thias presents an interesting problem. There can be no doubt, as 

 it appears, that H. hilgendorfi Traustedt, H. owstoni Oka, H. 

 ritteri Oka, of Japan, and H. o~kai, of the Pacific Coast of the 

 United States, are very close of kin. Furthermore, H. echinata 

 L., H. arctica Hartmr., H. villosa Stimp., and probably H. castan- 

 eiformis v. Dr., constitute another group of closely related forms 

 that is. however, sharply separated from the hilgendorfi group by 

 the difference in the stigmata already indicated. The echinata 

 group seems to be well represented in the Arctic regions, the Ber- 

 ing Sea and Alaskan waters, but thus far is unknown south of 

 Puget Sound on the American coast (H. villosa Stimp, Herdman 

 1898, Bitter 1901), or south of northern Japan (H. arctica 

 Hartmeyer 1906). On the other hand, none of the hilgendorfi 

 group are yet known from the region intervening between north- 

 ern Japan and northwestern United States. (On re-examining 

 certain specimens from Puget Sound which I (Ritter 1901) for- 

 merly assigned to //. villosa, I now find to be undoubtedly the 

 same as those from the coast of Southern California which I am 

 naming //. okai). In other words, the hilgendorfi group seems to 

 be replaced at the north on both east and west shores of the 

 Pacific by the rather distinct echinata group. Of course farther 

 collecting may bring to light members of the hilgendorfi group 

 in the Bering Sea and other Alaskan waters. It is desirable that 

 a closer study, both as to structure and as to distribution, should 

 be made of all these forms. 



About twenty-five specimens were taken from five stations, as 

 follows: 4552 Point Pinos light, S. 73E., 4 miles, June 9, 1904, 

 73 fathoms, green mud and rocks; 4554 Point Pinos light. S. 

 76E., 3 miles, June 9, 1904, 60 to 80 fathoms, green mud and 

 rocks; 4555 (practically same as 4554) ; 4557 Point Pinos light, 

 S. 25W., 3.1 miles, June 9, 1904, 53 fathoms, rock bottoms. 



