TTEROSOMATIDyE. 99 



body were membranous and formed a sort of fin extending 

 the entire length of the body; the skin was covered with 

 fine, depressed, parallel lines, with a regular row of small 

 round puncta in each interval ; the general colour was pale 

 brown, the tentacles being of a darker brown, and the 

 proboscis- like head was of a delicate pink. 



Fain. PTEKOSOMATLTLE. 



Lingual dentition ? Head without a proboscis ; 



mouth small, situated at the anterior extremity of the body ; 

 tentacles none ; eyes sessile on the upper surface of the 

 head. Body long and tapering, with two large, lateral, 

 horizontal, wing-like appendages, and extending behind in 

 a long, tapering tail. Gills ? Foot none. 



Shell none. 



Pelagian. 



The animal on which this family is established is naked, 

 gelatinous, and transparent, thickest in the middle, with a 

 very large, horizontal, lateral fin which commences at 

 the tail, and extends round the sides so as to form with the 

 body a shield, convex above, concave beneath ; the front 

 margin is the thickest and somewhat truncate, the hind 

 margin the smallest and thinnest ; the tail is cylindrical and 

 of a moderate thickness; the mouth, situated at the anterior 

 end of the body, is small and without a proboscis; the eyes 

 are elongated, sessile, and close together on the upper part 

 of tho head; the alimentary canal is red and visible through 

 the body, and is spirally contorted at the thickest part ; 

 the gills, anus, and organs of generation are unknown. 

 (Lesson.) 



