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. Cornuspira foliacea (Fig. 
488), though it occurs 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) 1s 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 foliacea. 
$. (Goès.) 
Fig. 489. — Astrorhiza limicola. 4. (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 
Seandinavian coast. Allied to Astrorhiza is a not uncommon 
