930 P. T. CLEVE, S. ATLANTIC PLANKTON. 



Scotland for 1896 p. 298 f. 15). There is no specific difference 

 between Castracane's and Hensen's species, the latter being 

 somewhat shorter only. This species occurred more or less abun- 

 dantly in nearly all samples from 41° S. 6 W. to 32° S. 91^ E. 



Corethron hispidum Castr. (Challeng. Rep. Diät. PI. XXI, 

 f. 3, 5, 6) seems to represent a coarser form of C. criophilum. 

 The denticulation of the awns seems not to be of specific value. 

 This form occurred in many samples, from 42" S. 3' W. to 

 43° S. 57° E. Whether it represents a distinct species or a 

 variety of C. criophilum, it has never been met with in the 

 northern hemisphere. 



Coscinodiscus (Actinocyclus) curvatulus Gkun. (incl. C. gyra- 

 tus Jan. Exp. Gazelle PI. V. f. 2, 3 and var. suhocellata Grün.). 

 This species occurred more or less abundantly and in many 

 varieties as a constant component of the plankton, from 41° S. 

 6° W. to 36° S. 89° E. It occurs in the northern Atlantic 

 and the Arctic Sea, on the whole rarely. 



Coscinodiscus excentricus Ehe. More or less sparingly from 

 43° S. 1° E. to 45 S. 32° E. 



Coscinodiscus lenti^inosus Janisch (Exp. Gazelle PI. IV f. 

 1, 2. A. S. Atl. P. LVIII f. 11). This species is very charac- 

 teristic of the antarctic regions and was found in all samples 

 from 43° S. 1° E. to 44 S- 48° E.; besides at 33°— 32° S. 

 90°— 91° E. 



Coscinodiscus lineatus Ehe. Occurred in many samples from 

 41° S. 6° W. to 34° S. 89° E. This form is so closely allied 

 to the large C. tumidtis, that the distinction is in many cases 

 difficult or impossible. 



Coscinodiscus minor Ehe. (A. S. iitl. PI. LVIII f. 39, 40; 

 PI. LIX f. 8, 9; PI. CXIII f. 10). This very small form was 

 found in many samples from 41 S. 6° W. to 34' S. 89° E. 



Coscinodiscus (Actinocyclus) Olivieranus O'Meara [^Act. Ol. 

 O'M. Linn. Soc. Journ. Bot. vol. XV p. 58 PI. 1 f. 7. A. um- 

 bonatus Castr. Challeng. Rep. Diät. PI. IV fig. 4. Coscino- 

 discus atlanticus Castr. 1. c. PI. III f. 7, probably also C. po- 



