Introduction to Animal Alorphology. 53 



habit.* Shell growth is slow, but injuries can be re- 

 paired. Monstrous forms are not uncommon.! 



Over 2,600 forms arc known, living and fossil, and of these 

 at least ten have survived from the Cretaceous period. They 

 occur in the seas of all climates, but are most abundant in 

 the superficial, littoral, and laminarian zones of tropical 

 seas. When they die they sink to the bottom, and hence 

 their dead shells are found at great depths. 



Reproduction occurs by the formation of gemmules either 

 with or without encystation (Truncatulina). In Miliola, 

 granular, possibly reproductive, bodies have been seen, and 

 Rotalian shells have been found filled with black spherules. 



Two orders are included: i. Imperforata, forms with 

 chitinous, arenaceous, or porcellanous shells, having only the 

 terminal aperture ; of these there are five families. 



i st. Gromidce, test membranous one-celled, mouth simple, 

 pseudopodia hyaline, the shell may be ovoid (GromiaJ), re- 

 tort-shaped (Lagynis), or globular with a wedge-shaped neck 

 (Sphenoderia), or the test may be scarcely detectible 

 (Lieberkiihnia). 2nd. Lituolidce, shell arenaceous, often 

 grained (Astrorhiza, Lituola), or smooth, fine-grained 

 (Trochammina.) Valvulina is intermediate, with a perforate, 

 vitreous, basal lamina, covered by the sand grains. The giant 

 fossils, Parkeria and Loftusia, arc related here. 3rd. Cor- 

 nuspiridce, calcareous, one-celled, discoidal, coiled shells, 

 iiiispira. 4th. Miliolida?, many-chambered, por- 

 cellanous ; opening simple ; whorls in one or several planes, 

 times irregular, sessile, adherent (Squamulina, Niibrcu- 

 laria' ;, or large, bottle-shaped (Dactylopora,^ Conodictyum), 

 iiscoidal (Orbiculina**), often Agathistegous (Miliola). 



Eozoon reached a large size, n:i<: ilc, with numerous radial 



canals, and a d l.amK-r wall. Many oilier Foraminifera 



make up rock m ulina, Miliola, and (il"l'i;vi ina arc rock-forming 



materials in the ' i Crctaccot: ;-ccti\v1y. 



hotomous 



acr. 



$ Sometimes made the type of 

 | Sometimes regarded as I ' miily Nn! 



5 Similarly scparat' ,ida?. .* 



