CH/ETOCEROS. 



4-1 



Sub-genus I. Ch.et/OCEROS. Valves elliptic, with awns not 

 arranged in a circle on the margin of the valve. 



a. b. 



Fig- 139. . Chcetoceros Wighamii. b. Chcetoceros Lorenzianus. 



ANALYSIS OF SPECIES. 

 Frustules closely united . . . . . . ch. armatum. 



C Apertures very large, suborbicular ; valves with 

 i Frustules leaving horns straight or very slightly curved . Ch, Wighamii, 



apertures between -J 



one another. j Apertures longly elliptic, lanceolate ; horns curved 



I. in the direction of minor axis . . Ch. paradoxum 



var. Eibenii. 



Ch. armatum, West. (T.M.S., i860, viii., p. 151, pi. 7, f. i 2; 



H.V.H. Atl., pi. 81, f. 1-4* Type No. 446), plate 18, fig. 603. 



