322 



BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



One species of this genus, sericeum Vanhoffen, now well known (ex- 

 cept for tentacles and otocysts), has been taken in the Bay of Biscay 

 (Browne and Fowler, 1906), off the west coast of Africa from Sierra 

 Leone to 42° S. (Vanhoffen, 1902), in the Malaysian region (Maas, 

 1905) , and in the eastern tropical Pacific (Bigelow, 1909a) . Whether 

 or not the Homoeonema typicum of Maas (1897), from off the Pacific 

 coast of Central America, is identical with it, has been the subject of 

 a good deal of discussion. Mayer (1910), following Maas (1905), 

 believes that it is. As I have previously pointed out, Maas, in his 

 original description of typicum, writes that there are more than four 

 times as many tentacles as canals — that is, more than 32 — and his 

 figure shows 41. Now, all recent studies, and the present series as 

 well, show that in sericeum the number of tentacles is determinate, 

 invariably 32 in adults. This number is present in moderate-sized 

 individuals, and is not overstepped even in very large ones How- 

 ever, the material on which Maas based his early account was not of 

 the best, and he himself suggests (1905) that it was its poor condi- 

 tion which led to his crediting it with so many tentacles. Unfortu- 

 nately Maas's original specimen is apparently no longer in existence, 

 so the question can never be settled absolutely. For the sake of uni- 

 formity I follow Mayer and use the name typicum (1913, p. 46) 

 instead of sericeum, as I formerly did. But Vanhoffen deserves credit 

 for first giving us an adequate account of this interesting genus. 



COLOBONEMA TYPICUM (Maas). 



Homoeonema typicum Maas, 1897, p. 22, pi. 3, figs. 1-3. Synonymy, Mayer, 

 1910, p. 385. 



Colobonema typicum — material examined. 



The specimens range from 16 to 33 mm. in height; they are all 

 more or less fragmentary. Only in two particulars will they add to 

 the previous accounts of this species, i. e., as regards otocysts and 

 length of the manubrium. Previously no otocysts had been found in 

 Colobonema, although a good many specimens had been examined — 



