OPHnJEOIDEA FEOM THE EOREAN SEAS. 459 



their inner edge ; tliey are in contact with tlie distal third of the 

 mouth-shield, and reach the generative slits. 



Jaws short and converging; tooth-plate large; mouth-papillae 

 eleven to each angle. They are small, short, and the outer are 

 broad; the innermost is sharply rounded and spearhead-shaped, 

 and the next are smaller and sharper, the others resembling the 

 outermost. There are four teeth, which are long, narrow, thin, and 

 rounded. 



The lower arm-plates are small, have a central longitudinal 

 projection, are longer than bi'oad, and have flat sides. The first 

 is the largest, and the next few are close, slightly broadest and 

 curved without. In mid arm (twelfth plate) they are elongated 

 heart-shaped or verging on the hexagonal, and are slightly sepa- 

 rated by the side arm-plates. 



The upper arm-plates. — The first and second are within the 

 notch : the one is very small, triangular, curved without, narrow 

 within ; and the other, much longer, is nearly square, and convex 

 from side to side. The third, shorter than the second, is broader 

 than long, is slightly overlapped by the second, convex from side 

 to side, especially at its distal end, where it is curved. The fourth, 

 broader than long, is broadly curved distally, where it is promi- 

 nent and convex ; it is narrower within, the proximal edge being 

 overlapped by the third plate. The succeeding plates become 

 more and more angular within, are broadly curved and project- 

 ing without, and are^ longer than broad. At the tip the plate is 

 very small and heart-shaped. 



The side arm-plates widely separate the others at the tip of 

 the arm, and separate the upper plates slightly at about the 

 eighth joint ; and the fourth upper plate is encroached upon 

 by the prominent broad flaps of the side arm-plates. The side arm- 

 plates are, on the whole, well developed, for the arms have large 

 sides ; they have large flaps, which are tumid and swollen below 

 and convex above ; they are close to the arm. 



Their free edge has spines on it, which are directed towards the end 

 of the arm, and near the disk, on the side of the arm, on several side 

 arm-plates, there is a solitary, sharp, short spine on the body of the 

 plate and remote from the others. On some side plates it is close to 

 the other s^^ines. The spines on the edge are short, small, close, sharp, 

 -slender, and some are flat ; they are rather irregular in breadth and 

 length, and a long one is usually innermost on the top of the arm. 

 Beneath, one or two spiculate sharp spines, longer than the others, 



