292 



THE ATLANTIC. 



[chap. v. 



appears to be the only new group of higher than generic value 

 which has come to light during the Challenger expedition. 



As a rule, these forms are extremely mi- 

 nute, although some of them approach in size 

 the smaller Eadiolarians. They consist usu- 

 ally of a single chamber of silica, varying 

 greatly in form, sometimes triangular, some- 

 times lenticular, and frequently nearly glob- 

 ular or flask-shaped ; with a single opening, 

 usually guarded by a beautifully formed and 

 frequently highly ornamented lip. The sur- 

 face of the shell is usually richly sculptured, 

 a favorite style of ornament being a series 

 of closely apposed and symmetrically ar- 

 ranged circular pits sunk deep in the siliceous wall, their inner 

 walls refracting the light, and giving the surface of the whole 

 a peculiar pearly lustre. The contents of the shell consist of a 

 mass of granular sarcode, with one or more large, well-defined 



Fig. 5S. — Challengeria. 

 Four hundred times the 

 natural size. 



Fig. 59.— Forms of the Challenger ida. 



granular nuclei, which color deeply with carmine ; and a num- 

 ber of dark-brown, sometimes nearly black, rounded compound 

 granular masses. It is singular that these deeply pigmented 



