APODA. 



89 



Order I. APODA. 



Udonella (Jolmst.). Body indistinctly ringed ; 

 no front sucker ; mouth inferior, longitudinal, 

 toothless ; no eyes ; hind sucker plain. 



A minute parasite on Caligus, which is itself a 

 parasite on the Holibut. 



U. caligorum. Fig. ,1 33; mag. j-. 



139 



140 



141 



138 



Malacobdella (De Blainv.). Body soft, broad, 

 without distinct rings ; no front sucker ; no pro- 

 boscis. Transparent parasites on bivalve Mollusca. 



M. grossa. Fig. 134 ; n. s. 



Tristoma (Cuv.). Body hard and convex above; 

 soft and flat beneath ; two equal disks in front ; 

 one larger behind. Parasitical on the Sun-fish. 



T. molce. Fig. 135 ; n. s. 



