1910.] AND NUDIBRANCHS OF BERMUDA. 143 



slightly darker than the rest of the body, having less of the 

 white. Near the tip of most of the branchiae there is an irregular 

 band of white ; distal to this there is a narrow band of the 

 ground-colour surrounding a central spot of white, which gives 

 the appearance of an opening at the end of each branchia. 



Extending from near the origin of each tentacle to the anterior 

 edge of the base of the rhinophore of its own side, is a series of 

 small tubercles. A similar row of tubercles runs laterally from 

 the posterior base of each rhinophore, while a short row appears 

 between the two rhinophores. 



The species is hardy, living for some time in confinement. 



The anal opening is lateral and is about one-third of the 

 distance from the anterior to the posterior end of the body. 



POLYCERELLA ZOOBOTRYON, Sp. n. (Text-fig. 10.) 



The genus Polycerella was established by Yerrill (80, p. 387 ; 

 82, p. 548) in 1880, when he described P. emertoni, taken at 

 Wood's Holl in 1875 and later at New Haven and Newport. 

 Since that time there have not been any additions to this genus. 



The present species was first observed by Mr. L. Mowbray in 

 December 1908, while he was trying to determine the reproduc- 

 tive stages of Zoobotryon pellucidics. At present it seems to live 

 on this bryozoan and not on any of the other organisms growing 

 near it. Several specimens were taken during my stay in 

 Bermuda, and in every instance they were found on this bryozoan. 

 The fact that Zoobotryon pellacidus has recently taken up quarters 

 in Bermuda, would seem to indicate that this habitat was also 

 recently assumed by this species of Polycerella, especially as this 

 bryozoan was under observation during the past summer and no 

 nudibranchs were seen upon it. It is also probable that this 

 nuclibranch did not come to Bermuda with Zoobotryon, because 

 the genus is very abundant in several localities and has been 

 thoroughly studied by Reichert (70), and yet no mention has ever 

 been made of a nuclibranch belonging to the Polycerella in con- 

 nection with it. 



Polycerella zoobotryon is a small nudibranch, from 5 to 6 mm. 

 in length and lg mm. wide. The body is thickest just anterior 

 to the branchial plumes. The shape is much as in Polycera — - 

 elongated, narrow, and about as high as broad. Body compressed, 

 smooth, sloping rather abruptly from the branchial plumes poste- 

 riorly until it merges into the long pointed tail, which is much 

 narrower and thinner, and nearly one-third the total length 

 of the animal. The head is blunt and squarish. The tentacles 

 are cylindrical, non-retractile, and one-fourth the length of the 

 rhinophores. 



The rhinophores are non-retractile, cylindrical, each having 

 from three to six cup-like, equidistant folds on the posterior 

 surface of its distal two-thirds. 



On the sides and dorsum of the body there are a number of 

 short clavate papilla?, the tips of which are translucent. The 



