APPENDIX. 431 



specimen, the openings were situated at the margin, in the 

 centre of each division. The play of colours of these 

 divisions depends upon some optical phenomena yet to be 

 developed. In the centre of the disc of those species 

 provided with these divisions is a broad, bright, and 

 polished umbilicus-like spot, which is invisible in those 

 not possessing internal partitions. This species was 

 found in sea water, along with the preceding. Diameter 

 1 -240th. 



765. BIDDULPHIA pulchella. Shell-like lorica quadran- 

 gular, compressed, and having three to five small obtuse 

 lateral processes. Found, living, in the sea, near Cuba, 

 &c., and fossil in the chalk marl of Greece. Diameter 

 l-290th. 



766. COCCONEIS oceanica. Shell-like lorica elliptical, 

 sub-orbicular, the back slightly convex, externally marked 

 by simple, curved, and concentric lines. This species is 

 not undulated, nor transversely striated. Found, with 

 Grammatophora oceanica, in sea water, near Callao. 

 Length 1-1 150th. 



767. COSCINODISCUS argus (1838.) Shell-like lorica 

 cellulose, the cells being large at the centre, and smaller at 

 the circumference, the order of the rays being often inter- 

 rupted. This is probably only a variety of Coscinodiscus 

 radiatus. Found fossil in the chalk marl of Caltanisetta 

 and Oran, and living, in sea water, near Cuxhaven. The 

 cells of the discs from Oran vary very much in size. The 

 ova are of a greenish colour in the living forms, which are 

 very rare. Diameter of fossil 1 -860th to l-290th; living, 

 l-580th. 



768. COSCINODISCUS eccentricus. Shell-like lorica 

 marked by small cells, which are disposed in eccentric 

 curved lines. It is found in the fossil state in the chalk 

 marl of Oran, in which condition, however, it is rare ; but 

 in the live state it is met with abundantly in sea water, 



