150 THE VOYAGE OF H.MS. CHALLENGER. 



In this small form the ventral line is almost as arcuated as the dorsal, so that the 

 outline is suborbicular or approximately elliptical. The extremities are very obtuse, and 

 the valve is delicately but irregularly punctated. 



Euodia radiata, n. sp. (Plate XII. fig. 4.) 



There is here represented a frustule which possesses a very different profile from the 

 preceding, but has the same delicate striation of radiating puncta. The apices possess a 

 hooked form, hence the varietal designation applied above. It was procured in the 

 Atlantic Ocean. 



Euodia ventricosa, n. sp. (Plate XII. fig. 5.) 



Parva, subradiantibus lineis punctulata ; linea dorsali admodum curvata, centrali late 

 convexa ; apicibus rotundatis. In Atlantico meridionali. 



This small frustule is ornamented with subradiating lines of puncta, which are disposed 

 in excentric curves. The dorsal line is strongly arched, while the ventral is less convex. 

 The extremities are bluntly rounded. 



The specific name has reference to the turgescence of the ventral margin. 



Euodia ventricosa, n. sp., var. nov. (Plate XII. fig. 6.) 



A variety which possesses a still more convex dorsal line than the typical species 

 just described, is here shown. The ventral line, on the other hand, is less arched, but the 

 character of the punctation and of the extremities is similar in both. 



Systephania, Ehrenb. 



This genus resembles the Stephanopyxis of Ehrenberg so strongly as to lead one 

 to the belief that, like Stephanopyxis, Ehrenb., and Cresivellia, Arnott, 1 they are 

 identical. Professor H. L. Smith is inclined to regard the Systephania as simply a valve 

 of Stephanopyxis, and although much may be said in favour of this view, the absolute 

 identity has still to be demonstrated. It is indeed true that, according to Ehrenberg, the 

 parallelism of the rows of cellules which cover the valve is to be regarded as characteristic, 

 since this was visible in the two species then known, namely, Systephania corona, Ehrenb., 2 

 and Systephania diadema, Ehrenb. ; ' but in a preparation kindly intrusted to me by Dr 

 James Rae, R.N., and made from material procured at Richmond, Virginia, five specimens 

 occur, one of which is figured on Plate IX. fig. 11. This undoubtedly constitutes a new 

 and very distinct species of Systephania, although the cellules that occur on the valve are 



1 Trans. Roy. Soc. Edin., vol. xxi. pt. iv. p. 538, pi. xiv. fig. 109. 



2 Ehrenberg, Mikrogeologio, pi. xxxiii. 15, fig. 22, and pi. xxxiii. 18, fig. 11. 



