RETORT ON TIIE DIATOMACEiE. 



77 



Chsetoceros janischianum, n. sp. 



Frustula cylindrica per cingulum binatim in laxam seriem conjuncta ; cornubus binis 

 prolixioribus mediis valvis assurgentibus et eleganter curvatis. In mari glaciali Antarctico. 



Tbis is without doubt the- most 

 elegaut typo of the genus Chaioceros. 

 It -was gathered from the surface of 

 the Antarctic Ocean in the form of 

 long seriate frustules, which were 

 united together in pairs by a common 

 belt. The valves are oval and notably 

 convex, and their awns, which are very 

 long and smooth, originate from their 

 centre, proceeding first almost at right 

 angles to the surface of the valve, and 

 afterwards interlacing by an elegant 

 curve with the corresponding awns 

 of an adjoining frustule. "Where this 

 interlacing occurs the awns are curved 

 horizontally and bent in such a manner 

 that each is alternately prolonged in a 

 direction at right angles to the plane 

 of the other. At the inferior valve of 

 the terminal frustule the two setae are 

 somewhat shorter, and are symmetri- 

 cally curved downwards. 



The belt already alluded to is 

 siliceous, and its presence is difficult 

 to reconcile with the independence of 

 the two frustules, nor is it easy to 

 imagine how it can disappear, and so 

 leave the latter free. 



The species has been named in 

 honour of Mr Janisch the well-known 



UiatOmiSlj. Chwtoceros ianischianum, n. sp. 



Cheetoceros curvatum, n. sp. 



Frustula solitaria ; valvis ovalibus, curvatis, superiori convexa, inferiori concava ; satis 

 a medio valvarum utrinque inferius curvatis, brevioribus ; zona quadruplo transverse lon- 

 gior quam latior. Ad meridiem insulae Heard. 



