336 DESCRIPTION OF \^Folycjaslrica. 



radiating striae), and with longitudinal central lines. Length 

 l-840th. On Marine Algae. Adi-iatic. 



CoccoKEis Adriatica. — Large, elliptic, with granular striae, trans- 

 verse on the disc ; radiating on the margin. Length 1 -696th to 

 1-4 80th. Trieste. 



C. Ifediterranea. — Size variahle, elliptic or elliptic -oblong ; disc 

 regularly dotted ; dots disposed both La transverse and in longitudinal 

 lines. Length 1 -840th to 1 -552nd. I^aples, Genoa. 



C. Peruviana. — Elliptic ; disc regularly punctate, with large 

 puncta in fours, disposed at greater distances. Length l-840th. 



Genus Coscinodiscxjs, (Ehi\) — Individuals solitary ; lorica bivalve, 

 discoid ; surface of disc cellular, with or without a central spot or 

 umbilicus ; without processes or defined margin. 



Coscinodiscus gives name to a family Coscinodiscece, see page 308, 

 which, together with the genus named, comprises Adinocyclm and 

 Actinoptychus ; it is a member of Ktitzing's tribe of areolate (cellular) 

 DiatomecB ; so called from the cellular character of their valves. 



Coscinodiscus approaches GaJUonella (Melosira), but is distinguished 

 by its cellular surface, and by not being concatenate. 



The members of this genus occur both in a living and fossil state, 

 and are marine in their habitat. 



C. patina. — Large, with moderately-sized cells, disposed in con- 

 centric circles. The cells decrease in size towards the circumference. 

 Fossil in the chalk marl of Zante, and alive in sea water at 

 Cuxhaven. The young and ^sdgorous specimens of live individuals 

 are completely filled with yellow granules, whilst the older ones 

 have an irregular yellow gTanular mass within them. Diameter 

 l-8G0thto l-240th. 



C. radiatus. — Large, marked with moderately-sized cells, disposed 

 in lines, radiating from the centre ; towards the margin the cells 

 become smaller. A very abundant fossil in the chalk marl of Oran ; 

 alive, in sea water, near Wismar and Cuxhaven. Diameter l-860th 

 to 1 -240th. (P. 14, figs. 39, 40.) 



C. Argus. — Cellular ; cells larger at the centre than at the cir- 

 cumference ; the order of the rays often interrupted. This is 



