MANUAL OF NATURAL HISTORY. 329 



cylindrical, truncate posteriorly ; proboscis 

 sub-conical, retractile ; caudal appendage 

 long, pyramidal, filiform, with the vent at 

 its extremity ; tentacles none. 

 4 FAMILY. Syphon-Worms (Sipunculidse). Body 

 cylindrical, elongate ; skin rugose ; proboscis 

 retractile ; vent at base of proboscis, sur- 

 rounded by a circle of tentacles. 



II. ORDER. SLUG-LIKE ECHINODERMS 

 (Cirrho-Vermigrada). 



Body molluscoid ; quinary division obscure ; mo- 

 tion effected by rows or groups of cirrhi, assisted by 

 contraction and extension of body ; mouth and anus 

 at opposite extremities of body ; mouth surrounded 

 by tentacles. 



I. SUB-ORDER. APODAL-HOLOTHURIANS (Apoda). 



Suckers undeveloped, or absent ? 



1. FAMILY. Vermiform - Holothurians (Synap- 



tidse.) Body cylindrical, vermiform, contrac- 

 tile, covered with numerous minute papillae ; 

 mouth surrounded by tentacles, which are 

 usually digitate or pinnatifid 



2. FAMILY. Sea-Gourds (Rhopalodinidse). Body 



elongate, rigid, brittle, covered with im- 

 bedded calcareous plates ; anterior extremity 

 cylindrical, tubular, posterior dilated sud- 

 denly, ovate, somewhat compressed, with a 

 slight keel on each of the two edges ; pos- 



