650 



ECHINODERMATA 



3. PsOLUS Oken. Lower surface of body forms a creeping sole on 

 which are the feet in rows; 10 oral tentacles; upper surface arched, 

 without feet, and usually with large calcareous scales: 13 species. 



P. phantapus (Strussenfeldt). Body thick, with 3 rows of feet; 

 anal region caudiform; color brownish, reddish, or yellowish; length 

 15 cm.: Cape Cod and northwards, from low water to 150 fathoms; 

 Europe. 



P. fabricii (Duben and Koren). Body wide, with 2 rows of feet, 

 one row on each edge of the creeping sole; color of upper side bright 

 red, the under side lighter; length 10 to 13 cm.: Cape Cod and north- 

 wards, in shallow water; Alaska; Europe; Asia. 



Family 3. MOLPADIIDAE. 



Body elongated, cylindrical and without ambulacral feet; 15 ten- 

 tacles usually present, which are either cylindrical or have minute 



branches ; tentacular 

 canals spring from 

 the radial canals and 

 usually have ampul- 

 lae: 8 genera and 

 about 50 species. 



Catjdina Stimp- 

 son. Body tapers pos- 

 teriorly into a more 

 or less evident tail : 8 

 species. 



C.arenata (Gould) 

 (Fig. 994). Tentacles 

 short, each with 4 

 branches at the tip; 

 color pink or pur- 

 plish ; length 10 to 17 

 Newport, Rhode Island, to the 

 locally common. 



Fig. 994 — Caudina arenata. 

 a dissection of the animal; 

 B, anterior end (Gerould). 1, 

 tentacles ; 2, ring canal ; 3, 

 gonad ; 4, ampulla of tentacle ; 

 5, respiratory tree ; 6, intestine ; 

 7, mouth ; 8, genital papilla ; 9, 

 cloaca ; 10, blood vessels. 



cm., about a third of which is ''tail 



Gulf of St. Lawrence, from low water to 18 fathoms 



Order 2. PARACTINOPODA. 



Holothurians without ambulacral feet, with 10 to 25 feathered, 

 digitate or simple tentacles, whose tentacular canals spring from tlie 

 ring canal, and with 1 to 50 Polian vessels; ampullae, radial canals, 

 respiratoiy tree, and Cmier^s organs wanting; mostly hermaphroditic: 

 1 family. 



