COSCINODISCUS. 



5 2 9 



ANALYSIS OF SPECIES. 



Valve with coarse granules, smooth space small 

 Valves having a smooth hyaline 



rounded space in the centre. ") Valve with very fine puncta, smooth space 



large 



o 



Q. 







- 2 

 i c 



C 



<D 



CJ 



3 

 O 

 Si 



r 



a 

 o 



0) 



II 





Alveoles 



in 



radiating 



rows. 



Valves with central alveoles of almost the same size as the 

 median alveoles of the valve . 



C. perforatus. 



C. nohilis. 



C. radiatus (Type). 



Alveoles 



in 



eccentric 



rows. 



Valves 



with 



central 



alveoles 



stellately 



grouped, - 



much 



larger 



than the 



median 



alveoles. 



Valves 

 with 



margins 



fur- 

 nished 

 with 

 apiculi, 

 alveoles 



in 



simple 



eccentric 



lines. 



Cells of f Valves without asymmetrical apiculi . var. Oculus Iridis 



the j 



rosette } Valve with two asymmetrical apiculi 



plane. L seen with difficulty 



Cells of f Valve with large robust alveoles 



the I 



rosette ; Valve with small and very delicate 



punctate, t cells 



Valve very small, apiculi very robust, alveoles in 

 irregular eccentric lines, the central much larger 

 than the others 



Valve rather large, apiculi delicate, alveoles in 

 regular lines . 



var. centralis, 

 var. asteromphalus. 



var. concinnus. 



I 



Valves having margin without apiculi, alveoles arranged in 

 eccentric lines forming fasciculi 



,. Alveoles arranged in rectilinear rows .... 



( Puncta large, forming distant and more or less radiating rows 



f Puncta in linear rows forming fasciculi . 



Valves 

 punctate. 



Puncta 

 very 

 fine. 



i Puncta forming lines divided clichotomously 



I Valve with puncta in radiating lines and shov 

 (. in addition, here and there, coarse granules 



C. decipiens Gr. 



C. excentricus. 



C. Kutzingii. 

 C. lineatus. 

 C. nitidus. 

 C. subtilis. 

 C, lacustris. 



C. punctulatus. 



Gro2ip I. Perforati. Valves with a smooth hyaline rounded 



space at the centre. 



C. perforatUS Ehr. (Mon. Ber. An., 1S44, p. 78; Ad. Schm. Atl., 

 pi. 64, f. 12*), plate 34, fig. 899. 



Valves with coarse radiant puncta, granular or polygonal, arranged in rows 

 of unequal length, the shorter terminating in an apiculus on the interior 

 margin of the valve ; centre of the valve smooth, hyaline ; diameter 9 to 1 2 

 c.d.m. 3*5 to 4 rows of puncta in 1 c.d.m. 



Marine and fossil. Found in Thames mud by Roper. Antwerp : Mud of the Scheldt (H.V.H.) 

 Maarstrand, Sweden. Ireland (O'Meara). 



LL 



