56 ON THE ECHINODERMATA OF 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 the 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, sixteen 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 out- 

 wards 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-papilla? and tooth-papillae ; and the teeth are in a double vertical 

 series with some accessory knobs, so that they resemble large tooth-papillae. 



The mouth-papillae 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, Avithin the distinct jaw-plate, there are three principal, 

 and one or more smaller, lowest tooth-papilla;. No satisfactory distinction, except that 

 of position, can be made between these tooth-papillae and mouth-papillae. Above the 

 three or more lowest tooth-papilla;, the others are in a crowded vertical series. They are 

 most numerous and small on either side ; and there are six or seven pairs of large, long, 

 pointed and irregular-shaped ones in the midst, and reaching up the jaw-plate to its upper 

 end, occupying the position of the teeth. The side of the jaws, close to the jaw-plate, 

 is occasionally covered with small and close papillae ; and there is a small accessory 

 papilla close to and at the side of the uppermost large ones. The upper part of 

 the jaw beneath the stomach is stout and tumid, and the jaw-plate is large and well 

 developed. 



There are two rounded knobs on the side of the jaw, above the attachment of the 

 mouth-papillae, which are in relation with the upper tentacle ; and the lower tentacle 

 of the angle has five or six short unequal-sized tentacle-scales, forming, with several 

 accessory scales, an obliquely placed curved wedge-shaped mass within the first lower 

 arm-plate and on either side of its oral margin. 



The lower arm-plates, there being six or seven within the disk, are mostly very broad 

 and very short; further out they are small and triangular, with an aboral projection. 

 They form but a small portion of the lower surface of the arm. The side arm-plates 

 meet below, from the first to the last, giving a broad and comparatively flat under 

 surface. 



The first lower arm-plate is unlike the others in shape, and it is elliptical in 

 outline and much broader than long ; the second, longer and very much broader than 

 the first, is somewhat rectangular ; its sides are slightly incurved ; and there is a 



