METAZOA MOLLUSCA. 235 



ored branchiae are arranged in six clusters, each cluster 

 consisting of many papillae. These branchiae are liable 

 to fall off, and sometimes a whole cluster is wanting, In 

 Flabellina (No. 520, F. janthina Angas), a related form, 

 the branchiae are numerous and tube-like, as they are 

 also in Spurilla neapolitana (No. 521). 



The branchiae in Glaucus longicornis Reinh. (No. 522), 

 are in the form of clusters of long slender filaments on 

 either side of the tapering body. These branchiae are 

 not only respiratory organs but are used for swimming 

 when the little creature with ventral side uppermost darts 

 through the water. 



Tethys leporina Linn. (No. 523), is a Nudibranch of 

 rare beauty. It is nearly transparent, with light and dark 

 red spots. The forward part is broad and has a delicate 

 fringe. The dorsal tentacles are leaf-like and the bran- 

 chiae extend down the body on either side. At the pos- 

 terior end the mantle is extended into an excurrent siphon. 

 Melibe (No. 524, M. fimbriata Aid. & Hanc.) has the 

 head differentiated from the body ; it bears two prominent 

 dorsal tentacles enlarged at the end. The body is cov- 

 ered with papillae, and along each side are large club- 

 shaped branchiae, which after the first pair are placed 

 alternately. 



Dendronotus arborescens Mull. (No. 525), is similar in 

 many respects to Eolis. When young it is nearly color- 

 less, but the adult is subject to much variation in color ; 

 usually, however, it is reddish, as seen in No. 525. 



The head is provided in front with branched append- 

 ages. Above are the dorsal tentacles which can be 

 withdrawn into sheaths. Along each side of the body are 

 the arborescent branchiae. The long tapering foot is 

 well adapted for clasping seaweed and is used in this 

 way as well as in crawling. 



Scyllaea marmnrata Aid. & Hanc. (No. 526), is a 

 small Nudibranch with two pairs of gills. The animal 

 resembles the Sargassum sea-weed in which it lives, and 



