CHARACTERISTIC DEEP-SEA TYPES. RHIZOPODS. 



161 



in number they become more circular, and finally conceal the 

 original nautiloid structure of the test. 

 The genus dates back to the miocene. 

 Except along the American coast, 

 where the genus appears to be a deep- 

 sea type, Orbitolites is found in shal- 

 low water ; it is quite common on 

 coral reefs. Comiispira foliacea (Yig. 

 488), though it occiu's in the arctic 

 seas in great abundance in compara- 

 tively shallow water, is not uncommon 

 in the pteropod ooze of the Caribbean. 

 Astrorhiza (Fig. 489) is a soft-tubed 

 type remarkable for the absence of any 

 definite aperture, the pseudopodia pos- 

 sibly finding their way out between the loosely aggregated sand- 



Fig. 488. 



Cornuspira foliaeea. 

 . (Goes.) 



Fig-. 489. — Astrorhiza limicola. \. (Brady. ) 



grains of which it is composed. It has been found off Block 

 Island and along the eastern coast of the United States, at mod- 

 erate depths. The great variety in the composition and consist- 

 ency of the test seems due in part to the material of the bot- 

 tom, and in part perhaps to the great stillness of the waters in 

 which it lives. This type was first described by Dr. Sundahl, 

 in 1847, from specimens found in shallow muddy water on the 

 Scandinavian coast. Allied to Astrorhiza is a not uncommon 



