310 MANUAL OF NATURAL HISTORY. 



Hind part of body with a large capsular ex- 

 pansion formed by a thin membrane, the 

 margin of which is sustained by two large 

 hooks and by a crown of simple or double 

 moveable spinous claws. 



4. Family. — Cotyloid - Worms (Octobothriidse), 



Mouth anterior and ventral, usually with a 

 tapering cirrhus ; fore part of body tapering, 

 hind part dilated, furnished above or on the 

 sides with six or more prehensible sucking 

 disks or acetabula, simple or armed with 

 hooks. 

 These Epizoa are parasitic on the gills of fishes ; 

 the genus Aspidocotylus, however, inhabits the in- 

 testines of a species of Cataphractus. The genus 

 Hectocotylus of Cuvier has been ascertained by F. 0. 

 Miiller to be one of the detached arms of the male 

 Argonaut containing the spermatic organs. (Vide 

 H. and A. Adams " Genera of Mollusca/' page 23.) 



5. Family. — Dish Worms (Capsalidse). Mouth with 



a sucker on each side ; body large, flat, disk- 

 like ; lower surface with a large cartilaginous 

 pedunculated sucker of adhesion on hind 

 part. 



6. Family. — Plaited - Worms (Aspidogasteridse). 



Body convex above, flat beneath, under sur- 

 face with a lamina folded on itself, the plaits 

 disposed so as to form numerous pits. 



7. Family. — Pedicellate - Worms (Pedicellariidae). 



Body disk-like ; oral orifice in centre of 

 lower concave surface, surrounded by three 



