COMB-JELLIES 

 GENUS Mnemiopsis 



157 



M. Leidyii. Resembles Bolina in general form ; often six to eight 

 inches in length; gregarious, thousands often being collected together; 

 exceedingly phosphorescent. 



ORDER CESTIDA 



GENUS Cestutn 



C. veneris, Venus's girdle. This singular animal, although not an 

 inhabitant of our seas, has its place in this group, and is shown here 

 because of its very curious shape. In form it is flat and ribbon-like. 

 Sometimes it attains a length of five feet, while in breadth it is but one 

 or two inches. The mouth is midway in its length and is opposite the 

 sense-organ or eye-spot. On each side of the mouth is a short tentacle 

 which protrudes from a sac. Four of the swimming-plates are small ; 

 the other four extend along the edge of the body. Cesium moves by 

 contractions of the body more than by the combs which fringe its edges. 

 It is very transparent, with a violet hue, and is so delicate that it is diffi- 

 cult to capture it uninjured. Its habitat is the Mediterranean Sea. It 

 may be seen among the zoological specimens in almost any museum. 



ORDER BEROIDA 



GENUS Idyia 



I. roseola. This species has an ovate body three to four inches in 

 height and about half as broad. Some individuals are larger. It has 



Cesium veneri*. 



