Dec. 1861.] 



Xarrtkal or Cochin Mud Bank. 2G7 



FAMILY YIII.-COSCIXODISCE.E. 



Genus COSCINODISCUS (Ehr.) 

 Coscinodiscus centralis (Ehr.) 

 Coscinodiscus Oculus Irides (Ehr.) 



C. pectinalis. (N. S.) Disk with irregularly radiating cellules, 

 smallest near the margin ; a hyaline border divided into numerous 

 compartments by radiating points. Diamr. 1.625." 



C. (? S.) Disk with a central umbilicus of seven 



elongated cells ; cells near the centre and margin smallest. In a 

 dry valve the angles of the hexagonal cells appear punctated at 

 the upper focus. Diamr. 1.500." 



C. ('? Sp.) Disk with a sub-hexagonal hyaline umbi- 

 licus having in the centre about 15 scattered punctse. Disk di- 

 vided into numerous zones by punctated lines radiating from 

 the umbilicus ; compartments containing 7 rows of parallel punctse 

 of which the median alone reaches the centre, margin broad, very 

 finely striated. Diamr. about 1.250". This is a very fine dia- 

 tom, but the specimen observed was broken, so that I am not quite 

 certain about the diameter. 



C. (? S.) Disk with smooth hyaline, umbilicus, cells 



in radiating rows of which some do not reach the centre, marginal 

 cells small, irregular, the cells from the centre half way to the 

 circumference gradually increase in size and have thick walls and 

 an irregular outline, the remainder are large, sharply defined, 

 hexagons. Diamr. 1.300 . 



Coscinodiscus ('? S. or ?) Disk divided into eleven compart- 

 ments by parallel rows of hexagonal cells of which the median 

 one alone is radial and reaches the centre of the disk, viewed 

 transversely the compartments have the oblique striation of Pleu- 

 rosigma, margin plain. Eleven short processes with expanded 

 and depressed extremities appear to be attached to the interior of 

 the connecting ring and opposite the centre of each compartment 

 Diamr. 1 375 '. 



Coscinodiscus (? S.) (or ?) Disk divided into 9 triangular 

 zones of parallel cells of which the median rows only reach the 

 centre, zones form a nonagon, of which the angles do not reach the 



