OF CONCHOLOGY. 299 



DESCRIPTIONS OP NUDIBRANCHIATE MOLLUSCA, IN- 

 HABITING POLYNESIA. 



BY W, HARPER PEASE. 



The following series of nudibranchiate mollusca was collected 

 by Mr. Andrew Garrett, and the drawings from which the fig- 

 ures are taken were made by him from the living specimens, and 

 may be relied on as strictly accurate. It will be noticed, that with 

 few exceptions all the Genera heretofore described from the 

 East Indies by Dr. Kelaart, Mr. A. Adams and Alder and Han- 

 cock, inhabit Polynesia. I do not discover, however, that any- 

 one species is common to the two localities. Our knowledge at 

 present is too limited to allow us to offer any idea as to the 

 distribution of genera and species over the tropics, or compare 

 them with those inhabiting the temperate regions. As the 

 anatomy of the genera is worked out, especially of the widely 

 diverse forms now included under genus Doris, which abound 

 over Polynesia, it will be found necessary to separate many now 

 confounded, especially those supposed to be common to the tropi- 

 cal and temperate provinces. It becomes more evident from 

 year to year, as our researches extend, that the distribution of 

 the genera of shell-bearing mollusca is confined to isothermal 

 lines, and such will prove to be the case with the above order, 

 with few exceptions. 



Genus DORIOPSIS, Pease. 

 Proc. Zool. Soc, London, 1860, p 32. 



The above genus, founded on a species inhabiting the 

 Hawaiian Islands, has been confirmed by two others from south- 

 ern Polynesia, which agree with the type in their generic char- 

 acters, though specifically widely distinct. 



The genus may now be characterized as follows : 

 " Body oblong, oval, depressly convex above, surrounded 

 equally on all sides by a fiat, depressed marginal mantle, cover- 



