468 PEOF. p. M. DUNCAN ON SOME 



the radial sliields, separating them centrally. The radial shields 

 are long, slightly curved, broad without where they join, narrow 

 within where they are separated by three scales and are rather 

 smaller. The disk is naked below ; and tlie generative slits are 

 large and long. 



The mouth-shields are small, longer than broad, and heart- 

 shaped ; they are angular orally, and well curved without, and the 

 madreporic, the largest, has a furcate process externally. The 

 side mouth-shields are large, triangular, narrow at the inner edge, 

 where there is incomplete junction, curved within, and large and 

 expanded at the arm. 



There are four mouth-papillse to each angle ; the innermost 

 two under the teeth, are large, blunt and long ; and the others 

 are long, spiniform, with a narrow base of attachment, and some- 

 times their base is broad, and there is a division into two. There 

 is a sharp spiniform upper tentacle-scale on either side. The jaws 

 are rather separate without, stout and short. 



The lower arm-plates are longer than broad, very slightly 

 curved without re-enteringly, and the corners are rounded. The 

 sides are nearly straight, and they slope towards the median line 

 orally. The inner edge is short, and soon becomes angular. 



The upper arm-plates are broader than long, slightly curved 

 without, and with a broad and rounded angle within. The side arm- 

 plates are well developed; and there are four short arm-spines, of 

 which the upper and lower are the thinnest, and the others are 

 stouter and blunter. They stand out radially, and have a narrow 

 base of attachment, a broad lower part, and a tapering end, and 

 they are striated and rough. Towards the end of the arm the 

 spines are more slender and spicidate, and they are there usually 

 three in number. 



The arms are about nine times the diameter of the disk, 

 whose diameter is -^ inch. The free edges of the side arm-plates 

 are wide apart, and naked skin exists between them on the side 

 of the arm. 



There are two small rounded tentacle-scales close together, one 

 on the under arm-plate and the other on the side arm-plate. 



Locality. Korean Straits, 51 fathoms. Collected by Capt. 

 St. John, E.N. 



In the British Museum. 



