OPHITJEOIDEA FEOM THE KOBE AN SEAS. 



453 



are rattier straight without, aud converge more definitely within. 

 All are slightly convex, and the madreporic is the largest. 



The side mouth-shields are small ; they are largest near their 

 inner junction, and they have a round small outer lobe, which 

 bounds the first tentacular opening aborally. The jaws are broad, 

 short, and are tumid near the plate, and they support nume- 

 rous mouth-papillae. There are from eleven to thirteen papillae, 

 all of which are small, to each mouth-angle : the first resembles 

 a true tooth, is the longest, and is angular and sharp ; the next 

 are smaller and are rounded, and the others are mostly little 

 narrow bands, more or less separated, here and there, and rounded. 

 There are four teeth, which are long, flat, narrow, and pointed. 



The arms, five in number, are about once and a half the length 

 of the diameter of the disk ; they are broad and high at the disk, 

 and taper gradually, and retain their great development at the 

 sides to their tip. 



The lower arm-plates within the disk have a more or less bold 

 longitudinal convexity with a broad expansion on either side ab- 

 orally. Broadest without, the plates are curved and are slightly 

 hexagonal, the side arm-plates being joined to the small margins 

 on either side of the distal end, and the rest of the side giving 

 support to the curved, short, flap-like set of ambulacral papilla). 



Beyond the disk the lower arm-plates lose the convexity, 

 are at first about as long as broad, and then become longer 

 towards the tip of the arm. They are hexagonal and broadest 

 aborally, and the oral edge, nearly straight, is the broadest, the 

 opposite one diminishing gradually to a point where the side arm- 

 plates come in contact, very close to the end of the arms. At 

 that part the lower arm-plate is more elongato-quadrangular and 

 broadest aborally. 



The lower arm-plates support on either side, aborally, a row of 

 thin, short, curved, flap-like processes, which are tentacle-scales. 

 They are usually five in number, are close, split up often aud very 

 irregular ; but those which are nearest the aboral part of the plate 

 are the largest, and the others diminish rapidly in size. These 

 scales diminish in size and number rather rapidly towards the 

 mid arm, where there is a rudimentary tentacle-scale, and it is 

 lost towards the tip. 



The upper arm-plates vary much in shape and size ; the first, 

 in the larger specimens, is within the angle of the radial shields, 

 and is rather convex, about as long as broad, rather pointed, and 



