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



adjacent plate having at first sight the appearance of being the only pair of true secondary 

 mouth-spines ; this is further enhanced by their being the most robust spines of the 

 series, as well as by their position. This character is, however, deceptive, as will be seen 

 from the foregoing remarks. The first pair of adambulacral plates is further noteworthy 

 on account of being separated by a conspicuous azygos shield-shaped plate, bearing 

 superficially the closest resemblance to the mouth-shield of an Ophiurid. This plate 

 extends to the interbrachial arc and is facetted laterally by the rudimentary marginal 

 plate, and in the lateral wall of the disk the cone-shaped plate, the so-called odontophore 

 of Viguier, or wedge-plate of Sars, is seen to stand upon it. 



The madreporiform body is very small but prominent ; it stands near the margin but 

 far above the cone-shaped plate just mentioned, and its surface is marked by two or three 

 deep, coarse, highly convoluted striations. 



A very distinct anal aperture is present in an excentric position. 



Colour when dried, an ashy grey, with distinct traces of a violet shade, which are 

 suggestive of that having been the original colour of the specimen. 



Locality. — Station 3. South-west of the Canary Islands. February 18, 1873. Lat. 

 25° 45' 0" N., long. 20° 14' 0" W. Depth 1525 fathoms. Hard ground. Bottom 

 temperature 37°'0 Fahr. ; surface temperature 65° - Fahr. 



Remarks. — This species is readily distinguished from all the other plated forms of 

 Brisingidse by the numerous spinelets of the dermal integument of the disk, also by 

 the character of these ; by the character and disposition of the adambulacral armature ; 

 and by the presence of the remarkable actinally superficial azygos interradial plate. This 

 congeries of characters is sufficient, in my opinion, to clearly mark the generic independ- 

 ence of the form, although the material at my disposal is unfortunately so fragmentary. 



