160 THE VOYAGE OF H.M.S. CHALLENGER. 



Coscinodiscus obovatus, u. sp. (Plate VIII. fig. 4 ; Plate XVIII. fig. 7 ; and Plate 

 XXII. fig. 9.) 



Valvis obovatis ; cellulis sequalibus ad marginem radiantibus, medio decussatis. In 

 mari Pacifico. 



The valves represented in the present figures all possess an oval outhne. The cellules 

 are arranged in rows which proceed from the periphery towards the centre, but around 

 this point the ornamentation varies in character, although it often assumes a simple 

 linear and decussate arrangement. In the form shown in Plate XVIII. fig. 7, which may 

 be regarded as the typical form, the margin is provided with an undulating line. The 

 frustules were all found in the Pacific Ocean. 



Coscinodiscus curvatulus, Grun., var. nov. (Plate III. fig. 10.) 



In this figure there is represented a very small disc which is richly covered with 

 granules, disposed in seventeen radiating lines, passing from the periphery to the 

 centre. Each line originates at a marginal indentation, and the granulation between the 

 lines is arrarjged parallel to them in each intermediate area. This valve can only be 

 regarded as a variety of Coscinodiscus curvatulus, Grun., 1 in which the lines, instead of 

 being straight, are slightly curved — a distinction which is of little importance. 



Coscinodiscus reniformis, n. sp. (Plate XII. fig. 12.) 



Frustulum reniforme ; striis radiantibus ; cellulis grandiusculis, ad centrum minuen- 

 tibus. 



This novel valve possesses a reniform outline, and is ornamented with radiating cellules 

 which decrease in size towards the centre. That it is a normal and not a teratolosical 

 form is shown by the circumstance that several specimens have been observed either 

 entire or in fragments from different and widely separated localities. 



Coscinodiscus lentiginosus, Janisch. (Plate V. fig. 4.) 



Mediocris, punctulorum lineis radiantibus, rariusculis, interruptis. In mari Antarctico. 



At Station 146, off Marion Island, lat. 46° 46' S., long. 45° 31' E., in a depth of 1375 

 fathoms, the valve here figured, along with many other discoidal forms, was obtained. The 

 entire collection has already been reported on under No. 207 of the interesting series of 

 Diatoms edited by Cleve and Moller, but I am not aware that the present species has 

 been referred to by Janisch in any other publication. Although the naming of a species 

 in a preparation is not regarded as equivalent to the publication of the form, yet the 

 designation lentiginosus given by Janisch is so apposite that it has been retained here. 



1 A. Schmidt's Atlas, pi. lvii. fig. 33 : " Die radialen Krumniungen haben in den beiden Schalen eine 

 entgegengesetzte Eichtung." 



