CHARACTERISTIC DEEP-SEA TYPES. — RHIZOPODS. 163 
Mexico, and Gulf Stream. The three (Fig. 493) or four armed 
varieties often come up in great quantities in the dredge, and at- 
tain a length of from 16 to 20 mm. Zr. abyssorum has a world- 
wide distribution ; 16 was discovered by the elder Sars, and de- 
Fig. 495. — Rhabdammina abyssorum. $9, (Brady) 
scribed in his first list of animals living in deep water off Norway. 
This species presents many interesting modifications dependent 
on external conditions, and its polymorphism seems remarkable ; 
it is triradiate, quadriradiate, or a 
straight tube, including all their possible 
combinations. A small straight form Fig. 494. —Rhabdammina line- 
of the genus, Zr. linearis (Fig. 494), is st: d$. (Bamdy.) 
also frequent near the 500-fathom line. 
One of the species of Lituolin:e, Reophax scorpiurus, attains 
a length of 10 mm. It builds its test loosely of siliceous sand 
Fig. 405. Fig. 405 a. 
teophax seorpiurus. $.  (Goés.) 
and sponge spicules. (Figs. 495,495 a.) A widely spread form 
crowded with nipple-shaped protuberances, Thurammina papil- 
