52 Introduction to Animal Morphology. 



are alternate in successive whorls, and from each 

 chamber a tube passes inward to the narrow inter- 

 cameral part of the whorl within (small Orbitolites). 

 In larger forms of this genus, each whorl canal is 

 horizontally divided into two parallel canals joined 

 by many vertical branches, and the chambers are 

 divided and displaced towards the surface, so that 

 each communicates with its canal by a double passage. 

 In the cycloidal Nummulites, each whorl not only sur- 

 rounds the margin of the one within it, but invests its 

 surface, thus producing rings of new chambers round 

 the margin, while the superposed laminae, lying close 

 together on the surface, are separated by fine inter- 

 lamellar spaces. There is thus a layer over the 

 central cell for each cell between it and the margin. 

 Each chamber communicates with its neighbours of 

 the same whorl by several openings, and with those 

 inside and outside by large diverging canals. Through 

 each lamina pass fine parallel canals, except where 

 the laminae are joined by imperforate radial pillars. 

 In these the sarcode is moulded to the cells, sends 

 stolons through the canals, and pseudopodia through 

 the marginal openings. 



Living forms range from 0.3" to 0.002''. Some 

 fossil forms are much larger, several inches in 

 diameter. Some sessile irregular forms also reach 

 large sizes. Thus, Carpenteria consists of lobed conical 

 masses, ceasing early to grow spirally, and attached 

 to shells, &c. ; dense sarcode protrudes through the 

 apical opening with siliceous spicules (r). Polytrema 

 is a scaly red encrustation on shells, &c., with no 

 spicules. The oldest known fossil, Eozoon, from the 

 Laurentian Serpentines of Canada, resembled these in 



