62 ON THE ECHINODERMATA OF THE 



OPHIOGLYPHA ROBUSTA, Ayres, sp. Plate IV, Figs. 5-7. 



Ophiolepis robusta, Ayres, Proc. Best. Soc. N. H. iv. 1851. 

 Ofhlura squamosa, Liitken, Vid. Moddel., Nov. 1854. 



An Ophioglypha with arms very finely tapering, and disk with regularly arranged 

 scales of nearly equal size. Mouth-shields ovate shield-shaped ; length less than, or 

 at most only equal to, their breadth ; length much less than the distance from the 

 margin of the disk. Papillae of the disk-incision very short and stout, often grouped. 

 Under arm-plates broadly heart-shaped ; one tentacle-scale. 



This species was obtained at various stations, as indicated in the list of localities ; 

 and though neither the abundance nor the size of the specimens was remarkable, 

 several good series were collected. The characters which have been regarded as 

 " specific " are remarkably constant ; and no essential difference can be traced between 

 these Arctic forms and specimens taken from the coast of Maine, U. S., with which 

 they have been compared, excepting that in the northern Ophiurans the arm-spines are 

 longer and somewhat more delicate, and that the outer margin of the under arm-plates 

 is more arched, and the reentering angle is far less developed, being even altogether 

 untraceable in certain specimens. In some large examples the upper arm-plates are 

 very markedly hexagonal. Although this deviation is very constant, the foundation of 

 a " variety " on the strength of such characters alone, is hardly justifiable. 



The arm-spines are moderately stout and tapering, the upper one being flattened 

 and much larger than the others. 



In most of the specimens under present consideration the under arm-plates are 

 well separated from one another by the side arm-plates, and do not overlap, although in 

 one individual from Discovery Bay the first ten impinge distinctly, in consequence of 

 their side arm-plates not meeting. This feature at the basal portion of the arm has 

 been noted by Dr. Liitken as occurring in large specimens from Greenland, whilst he 

 remarks at the same time that in none of the Danish examples examined by him do 

 the under arm-plates touch. 



Coll. Feilden. Discovery Bay, 25 fins., hard bottom ; Eichardson Bay, 70 fms. ; 

 Hayes Point, 35 fms., bottom temperature 29 0- 5, and also at 25 fms. ; Franklin-Pierce 

 Bay, 15 fms., bottom temperature 25'5. 



Coll. Hart. " Winter quarters," Discovery Bay ; Franklin-Pierce Bay, 13-15 fms., 

 bottom stony. 



The largest specimen was taken by Capt. Feilden in Franklin-Pierce Bay, the 

 diameter of the disk (dried) being 10 millimetres. 



The scaling of the upper part of the disk is very variable in its pattern, relative 

 size, and colour. In one specimen the usual smaller scaling is in the centre, and the 

 larger around ; but the central scale is almost circular in outline, and is surrounded 

 by smaller ones, some of which are triangular, with the apex broadly rounded and the 

 intermediate one rhombic. This produces a curious rosette, eminently crinoidal in 

 its configuration, but flat. The ornamentation of grains of calcareous matter on these 

 scales is very beautiful ; it radiates in numbers of separate and close lines of granules 

 from the centre of the central scale to the outside of the bluntly triangular scales ; and 



