G 



Dorsal side composed of large, quadrangular, squamose plates, 

 that encircle the arm as far as the ambulacral groove of which 

 they form the margin. They are divided in the upper portion 

 of the ray by a median suture. 



Dorsal, ray plates fimbriated on the free margins. 



All plates are perforated by minute, closely arranged pores. 



SQUAMASTER ECHINATUS (N. Sp.). PI. i, fig. i. 



Body small. Rays long, slender, not vv^idening at the base ; 

 regularly tapering to a sub-obtuse point. Dorsal side covered 

 by thin imbricating plates, with free external margins which are 

 edged on the outer and lateral sides with closely arranged, long, 

 slender, filiform spinules, that articulate into minute rounded 

 sockets, which are scalloped out of the margin of the plate ; they 

 are slightly longer than the exposed portion of the plate, and are 

 placed about their own diameter apart. 



Ray divided into about forty segments or articulations by the 

 encircling, dorsal plates ; these grow rapidly narrower near the 

 body, and are divided by a dorsal suture running along a raised 

 median ridge which extends about two-fifths of the length of the 

 ray from the body out, where it gradually disappears with the 

 last divided plate ; the rest are entire. These plates are quad- 

 rangular, and have their inner corners articulated into the socket 

 formed in the dentate lateral extensions of the ambulacral series. 

 They are ornamented on each side by two or three closely ar- 

 ranged, sub-parallel, very fine ridges, that commence near the 

 dorsal line at the free margins and extend diagonally backwards 

 across the plate towards the inner lateral articulated corner. 

 Ambulacral groove furnished with opposite, irregularly quadri- 

 lateral, ambulacral plates, divided by a median suture which is 

 crossed alternately by one long and one short suture. 



The superior plate of each pair has the greatest extension 

 laterally, while in the inferior it is the direction of the median 

 line, it being about twice as long as the superior, which, however, 

 is but slightly broader. 



