298 



LOWEi; IXVKUTEBUA TF.S. 



Leaving llieso curii)us parasites, whicli, so far as known, are unri']ircsente(l on our 

 shores, we come to forms which undoubtedly belong to the Nudibranchiata, and which 

 lead free lives in the seas of all parts of the globe. 



Passing by the Phyllidid-e, a small family of tropical and semi-tropical forms, in 

 which the gills are either absent or enclosed between tlie mantles and the foot, we 

 come to the Ki.ysiid.i:, in which the body is shaped much like a common garden slug, 



Fic. 3'3G. ~ Pmttolhnax caplfans. 



the gills have disappeared, and the tentacles are simple or absent. This family is 

 represented in our figures by PontoUmax ccqntmis, a form only a third of an inch in 

 length, found on the coasts of northern Euro|ic. It lives between tides, feeding on 

 minute algre, and lays its eggs in small, pear-shaped capsules, each containing on the 

 average about one hundred eggs. Pontolimax zouata occurs on the New England 

 coast. In I'Jh/skt, the typical genus of the family, the tentacles are well developed 

 and the sides of the body aie expanded into a pair of wings, which stop just behind the 

 neck. Elysia viridis of the Euroiiean seas is of a green color, as is also our New England 

 E. c/ilorotica, and the closely allied Eli/sidla catuNiis. These forms aie not uncom- 

 mon, creeping .■il)out on the eel grass (Zosti'ni) of our northern coasts. 



Fig. 337. — Elt/sia viridis. 



In the EoLiD.K, a much larger family than the last, the gills, which may be 

 lammated, pa])illose, or like plumes, are arranged along the sides of the back, while the 

 tentacles are capable of being retracted into sheaths. The genus Tei-ffipes, which is 

 rcjn-esented by a little species common upon the stems of hydroids, received its name 

 from old Forskal, from a belief that it walked upon its back, using its gills as locomo- 

 tory organs. The brauchiaj are eight in number, arranged in a single row of four on 



