EEPOET ON THE KERATOSA. 



51 



form of the section may be compared with a battledore, though the stem must be 

 called very thick, and besides ends with a basal extension ; but only as regards the plane 

 of the section, the whole not being compressed, but of a massive form and of rather 

 roundish outline. The colour of the incrustation is not white but pale greyish ; and the 

 colour of the skeletal fibres is only straw-yellow. Again, I cannot call the outer surface 

 of my specimen unconditionally even ; at anyrate the surface of the skeleton devoid 

 of soft parts is denticulated; these denticulations are not, however, the terminal points of 

 single fibres, but whole networks in the form of sharp-pointed projections. All these 

 peculiarities together, and particularly the formation of sharp-pointed projections on 



Fig. 1. — Skeletal fibres of Coscinoderma cmifra<josum. 



the surface of the skeleton, quite absent in Coscinoderma lanuginosum, Carter, necessitate 

 the establishment of a new species. In the accompanying diagram a portion of the 

 skeleton is represented in order to show the manner in which the fibres interlace with 

 one another. The fibres themselves are entirely devoid of any foreign enclosures, and 

 their average thickness is '0 1 5 mm. The species is represented in the collection by a 

 single specimen, dredged by H.M.S. " Porcupine." 



Colour. — Outer surface greyish, parenchyma pale grey-yellowish, skeletal fibres 

 straw-yellow. 



Habitat. — H.M.S. " Porcupine," Station 13, 1870, ofi" the coast of Portugal; depth 220 

 fathoms. 



Coscinoderma denticidatimi, n. sp. (PI. VI. fig. 4). 



This species, also represented by a single specimen, agrees with Coscinoderma con-' 

 fragosum as regards the formation of sharp-pointed projections of the skeleton, though 



