78 



THE VOYAGE OF HALS. CHALLENGER. 



This isolated frustule possesses four awns or cormia, originating from the centre of 

 the concavo-convex valves. Those from the externally concave or inferior valve are slightly 

 tortuous, while all are short, and bent downwards. The zonal side 

 is about four times as long as broad. 



The specific name has reference to the curvature of the valve. 



Chsetoceros criophilum, n. sp. 



Frustula oblonga, valvis convexis (superior inferiori convexior) ; 

 setis spinulosis longissimis a rnediis valvis orientibus, et inferius 

 curvatis. In mari Antarctico. 



In this Diatom it is to be noted that the two valves differ from 



each other in two important respects : (1.) The height of the 



c hwtoceros curvatum, n. sp. upper seems to be double that of the lower; and (2.) the upper 



valve is decidedly more convex than the lower. The setse are very long, spinulose, 



.spring from the middle of the valves, and are slightly curved near their origin. In the 



Chatoceros criophilum, n. sp. 



Chcetoceros convolutum, d. sp. 



course of their length they are ornamented with sparsely and somewhat irregularly 

 disposed apiculi, all of which are directed towards their distal extremities. 

 This species was gathered near the ice-barrier of the Antarctic Ocean. 



Chaetoceros convolution, n. sp. 



Valvis ovalibus, una convexiuscula, altera plana ; setis longissimis a media valva 

 convolute orientibus. In mari Antarctico inter insulas Kerrmelen et Heard. 



