CHARACTERISTIC DEEP-SEA TYPES. RHIZOPODS. 



L63 



Mexico, and Gulf Stream. The three (Fig, 493) or tour armed 

 varieties often come up in great quantities in the dredge, and at- 

 tain a length of from 16 to 20 mm. R. abyssorum has a world- 

 wide distribution ; it was discovered by the elder Sars, and de- 



Fig. 4!*.'j. — Rhabdammina abyssorum. *. (Brady.) 



scribed in his first list of animals living in deep water off Norway. 

 This species presents many interesting modifications dependent 

 on external conditions, and its polymorphism seems remarkable ; 

 it is triradiate, quadriradiate, or a 

 straight tube, including all their possible 

 combinations. A small straight form 

 of the genus, R. linearis (Fig. 494), is 

 also frequent near the 500-fathom line. 



One of the species of Lituolinse, Reojjhax scorpiurus, attains 

 a length of 10 mm. It builds its test loosely of siliceous sand 



^^;r?...!S t .Ah i i , :gji/i 



Fio-. 404. — Rhabdammina line- 

 aris. |. (Brady.) 



Fio-. 40o. 



Fi«\ 495 <r. 



Reopbax seorpinrus. |. (GoeV) 



and sponge spicules. (Figs. 495, 495 a. ) A widely spread form 

 crowded with nipple-shaped protuberances, Thurammina />"/>!?- 



