1899.] NATURAL SCIENCES OF PHILADELPHIA. 519 



Trippa areolata (A. and H.) Bergh. 



This animal affords an extraordinary example of mimicry. It 

 so exactly resembles a shell or old stone overgrown with green 

 and blue seaweeds and with sponge that it is absolutely invisible 

 when crawling on such objects. When the specimen which I 

 caught was placed in a basin with shells it took up a position on 

 an old Strombus, and could not be distinguished from the growths 

 and accretions by which it was surrounded. 



The body is deeply indented with cavities like those made by 

 worms in stones. The rhinophores and branchial rosette are 

 grayish brown, and in spite of their size, inconspicuous. 



This animal is described by Alder and Hancock ( Trans. ZooL 

 Soc, Vol. V, 1864) as Doris areolata, and recorded from the east 

 coast of India. Bergh refers it, with a query, to his genus 

 Trippa. The dentition shows that it undoubtedly belongs to this 

 genus. There are no jaws, but the radula resembles that of T. 

 ornata Bgh. There is no central tooth, but about forty laterals 

 on each side. The innermost teeth are very small, but increase in 

 size up to the fifteenth, after which they become equal, except 

 the two or three outermost, which are reduced. The transverse 

 rows are nearly straight at the sides, but bend downward in the 

 middle. 



Doris setosa Pse. 



Bergh, in Semper's Reisen, II, 2, supplement Plate G, gives a 

 figure of Doris setosa from Pease, Proc. ZooL Soc, XVIII, 1860, 

 p. 26, which he seems unable to assign to any of his genera. 

 Last July I captured at Mulifauua, Upolu, three specimens of an 

 animal which, except in color, appears to agree with Pease's plate. 

 The largest specimens were an inch long. The upper surface, 

 branchial rosette and rhinophores were brownish yellow with 

 darker bi'owu spots. The under surface of foot and mantle 

 whitish. The branchial star was ten plumed and protected by 

 two lateral lobes; the anal tube prominent. The whole dorsal 

 surface covered with villous projections, which contain spicules, 

 and can be scraped ofi^, leaving a smooth surface. The radula 

 consists of five rows of simple hamate teeth. There is no central 

 tooth and the formula is 19 (or 18) 0. 19 (or 18). Jaws are 



