NO. 4 FRASER : HYDROIDS 7 



Remarks. — The colonies of Clytia similis in which the zooids, both 

 nutritive and generative, develop singly from the stolon, resemble those 

 of C. johnstoni (Alder), in every character except the shape and size of 

 the hydrotheca. In C. similis, the hydrotheca is much longer and more 

 slender than that of C. johnstoni; the marginal teeth are sharper and 

 more deeply cut. The colonies with two or more hydrothecae and one or 

 more gonangia growing from the pedicel, bear almost as great resem- 

 blance to those of C. minuta (Nutting), although they are not so slender. 

 Here, too, the hydrothecae are different; in C. minuta, they are much 

 smaller, with the length and breadth more nearly equal ; there are fewer 

 marginal teeth; the pedicels are more extensively annulated; the cor- 

 rugations on the gonangium are closer together and hence more numer- 

 ous. To get a duplicate of the hydrotheca it is necessary to go to another 

 genus, Gonothyraea, in the species G. gracilis (Sars). 



In most species it seems to be quite sufficient to find a close resem- 

 blance to one other species, but here similarity shows up in 3 species not 

 very closely related to each other. The difference is least in the case of 

 C. johnstoni, and the distribution range of this species makes it more 

 readily possible to suggest that C. similis has been derived directly from 

 that species. 



Genus GONOTHYRAEA 

 Gonothyraea gracilis (Sars) 



Laomedea gracilis Sars, Beret, om in Zool. Reise, 1851, p. 18. 

 Gonothyraea gracilis Fraser, Atlantic Hyd., 1944, p. 148. 



Distribution. — 1 mile southwest of Cape la Vela, 10-13 fathoms; 3 

 miles north of Coche Island, 21-22 fathoms. 



These locations are much to the southward of the records from the 

 Florida and Louisiana coasts, and possibly show the route taken to the 

 locations in the Eastern Pacific where it has been collected. 



Genus OBELIA 

 Obelia equilateralis Fraser 



Obelia equilateralis Fraser, Allan Hancock Pacific Exped., 4(1): 



1938, p. 36. 



Fraser, Atlantic Hyd., 1944, p. 157. 

 Distribution. — Caledonia Bay, hand line on rocky reef. 

 This location is quite a long way from the Louisiana coast, but still 

 farther away in the other direction from Santa Elena Bay, Ecuador. It 

 helps somewhat to link up the two. 



