a new Genus of OpMuroidea. 189 



naked radial shields, have a stout flaccid derm covered with 

 excessively minute scales. The radial shields are small, 

 pear-shaped, narrow, and angular within, where they slightly 

 overlap, and broad and curved witliout, with a free edge 

 there ; they are very distant, and bound the incision for the 

 arm on either side (y% inch long). Many small scales, some 

 elongate and others extremely small and oval, are situated be- 

 tween the radial shields and the arm. There are no radial 

 scales with spines ; and the generative plates are hidden. 



The mouth-shields are small (-^ inch long), about as broad 

 as long, somewhat pentagonal, broadest without, angular 

 within, the aboral edge being nearly straight. The sides of 

 the shields are rather straight and are at right angles to the 

 aboral margin for some space, and then they slope inwards to 

 the oral point. An accessory plate exists, in some, between 

 tlie oral angle of the mouth-shield and the side mouth-shields. 

 The madreporic plate is cribriform. 



The side mouth-shields are rather large, do not unite closely 

 within, are long and rectangular, being widest at the side 

 angle of the mouth-shield, where they are more or less pointed, 

 curved, and rounded off. 



The generative slits are short and linear ; the edges are close 

 together, and have on them small, flat, rounded spinules, six- 

 teen or more on each ; they are distant from the mouth- 

 shields and from the margin of the disk ; and a series of fine 

 scales passes outwards from their distal end, by the side of the 

 arm, to the margin. Other minute scales are in a patch on 

 the oral side of the slits. 



The jaws are rather long, stout, tumid and bossed, and 

 form rather a sharp angle ; and the lower edge of the jaw- 

 plate is broad and stout ; the angular spaces are wide and 

 large ; and the tentacles are very well developed. 



There are mouth-papillee and tooth-papillse ; and the teeth 

 are in a double vertical series with some accessary knobs, so 

 that they resemble large tooth-papillte. 



The mouth-papillee are numerous, fourteen or fifteen to each 

 angle, small, much joined together at their bases, irregular in 

 size, shape, and number, short, and never very broad. At 

 the apex of the angle, within the distinct jaw-plate, there are 

 three principal and one or more smaller lowest tooth-papillae. 

 No satisfactory distinction, except that of position, can be 

 made between these tooth-papillse and mouth-papillce. Above 

 the three or more lowest tooth-papillae the others are in a 

 crowded vertical series. They are most numerous and small 

 on either side j and there are six or seven pairs of large, long, 

 pointed and irregular- shaped ones in the midst, and reaching 



