298 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



Count Castracane, in his report on the Diatoms col- 

 lected by H.M.S. "Challenger," established (p. 813) a 

 new genus, Corethron, for certain forms collected in the 

 Antarctic Ocean. They are allied to Bacteria strum, and 

 the author characterises his genus as having frustules 

 cylindrical, free (?) ; valves convex, surrounded by a 

 corona of radiating awns. 



He divides it into two sections, one with smooth, the 

 other with echinated awns. A form which occurs rather 

 sparingly in Mr. Thompson's gathering seems to be 

 intermediate between the two; for the awns of one valve 

 are flat, and their margin distinctly dentate ; the awns 

 of the other valve appear smooth. But the main feature 

 of the form is the presence of peculiar appendages round 

 the upper valve, intermingled with the awns. They are 

 flexuose, flattened and expanded at base and apex, the 

 latter bearing a double claw, set at right angles to its 

 pedicel. The specific name has reference to these. 



Corethron unguiculatum, n. sp. PI. XIX. 



Frustule lenticular to spherical ; valve varying from con- 

 vex to hemispherical, smooth ; awns erect, spreading, or 

 recurved. Those of one valve flattened, dentate, and 

 intermingled with flexuose clawed appendages ; those of 

 the other valve smooth. 



Antarctic plankton, near South Shetland Islands. 

 For list of Diatoms observed at the surface, station 

 157, in the Antarctic, see — 



Report on the Scientific results of the Voyage of H.M.S. 

 " Challenger." (Summary of Results.) Part I. (pub- 

 lished 1895), p. 517. 



Besides verifying (and correcting) the list originally 

 compiled by Rattray, about 30 species, I was 

 able to add thereto about 18 species. 





