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



interior of the frustule, as maintained by Kiitzing, but that, on the contrary, the walls 

 are thick at this place, so that the general opinion that in Diatoms the siliceous nodules 

 are more or less solid protuberances is here confirmed. 



The size of this new species, which has been named in honour of Mr John Murray, the 

 Editor of the Challenger Eeports, is not less than 200 m. 



Glyphodesmis challengerensis, n. sp. (Plate XVIII. fig. 13.) 



Magna, medio constricta ; apicibus productis cuneato-rotundatis ; pulvinulis ter- 

 minalibus lsevibus ellipticis ; nodulo centrali erectiore in area lsevi elliptica ; punctulis 

 quadrato ordine dispositis ; linea axialis in valva latior. Ad mare Philippinarum. 



This frustule, which is represented in its valval and zonal aspects, possesses small 

 terminal cushions and a central nodule which are decidedly elevated. The central nodule 

 is not a mere' granule like that of the Naviculacese, but exists in the form of a large 

 elevated process with a flattened top. This nodule and the terminal cushions are the points 

 by which the adjoining frustules of a series are united to each other. 



The valve presents a median constriction and two lateral protuberances. The 

 extremities are prolonged but rounded. The granules, which are punctiform, are disposed 

 in a quadrate manner in parallel rows, and the longitudinal axis is represented by two 

 rows of dots somewhat further apart and more prominent than those in the adjoining rows. 



Glyphodesmis margaritacea, n. sp. (Plate XVIII. fig. 10.) 



Valvis ellipticis ; granulis distinctioribus quadrato ordine dispositis et transverse 

 per plicas distinctis, ad apices et ad centrum areae lseves, in area centrali noduluin sub- 

 obscurum. Ad Zebu, in mari Philippinarum. 



This frustule, which is only represented in its valval aspect, possesses a very elegant 

 elliptical form. The valve is ornamented with beautiful round granules disposed in 

 a quadrate manner. It is crossed by transverse folds, and in its centre as well as at 

 its extremities there are smooth areas which, however, are less clearly defined than in the 

 two preceding species. In the central area the nodule is not prominent, and greatly 

 resembles that of Glyphodesmis cximia, Grev., but the nature of the valvular sculpturing 

 is'quite distinct. 



The frustule figured is of large dimensions. 



Glyphodesmis_(?) an Dimeregramma (?) sp. (?) (Plate XIX. fig. 10.) 



This figure represents a series of small frustules seen in the zonal aspect, but, since the 

 genera Glyphodesmis and Dimeregramma can be distinguished only when viewed in their 

 valval aspects — the essential distinction being found in the presence of a central nodule 



