650 



ECHINODEEMATA 



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 (Diiben 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. 



CAUDINA Stimp- 

 son. Body tapers pos- 

 teriorly into a more 

 or less evident tail : 8 



B 



species. 



C.arenata( Gould) 

 (Fig. 994). Tentacles 

 short, each with 4 

 branches at the tip; 

 color pink or pur- 

 plish ; length 10 to 17 

 cm., about a third of which is "tail": Newport, Rhode Island, to the 

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



Fig. 994 Caudina arenata. 



A, a dissection of the animal; 



B, anterior end (Gerould). 1, 

 tentacles ; 2, ring canal ; 3, 



onad ; 4, ampulla of tentacle ; 



, respiratory tree ; 6, intestine ; 

 7, mouth ; 8, genital papilla ; 9, 

 cloaca ; 10, blood vessels. 



ORDER 2. PARACTINOPODA. 



Holothurians without ambulacral feet, with 10 to 25 feathered, 

 digitate or simple tentacles, whose tentacular canals spring from the 

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

 respiratory tree, and Cuvier's organs wanting; mostly hermaphroditic: 

 1 family. 



