OF THE MERGUI ARCHIPELAGO. 



89 



the form of well-developed crests ; they are rather close, and the 

 intervening muscle is well developed. These are Ophiophragman 

 characters. But the width of the mouth-frames is greater, and 

 the height of the interbrachial rims is less than in O. Wurde- 

 manni, Lym. Probably the very narrow mouth-shield determiues 

 the narrowness of the space between the interbrachial rims of 

 the mouth-frames, as seen from above. 



2. The first three arm-bones within the disk, as seen from above, 

 after the removal of the roof of the disk, resemble those of Opliio- 

 phragmus ; but those further out resemble those of Ampliiura. 



3. There is a peristomial plate, and the character is not Ophio- 

 phragman, but it resembles that of Hemipholis. 



4. The genital plate is long and slender, and simply knob- 

 headed, and the generative scale is long and slender and longer 

 than the plate. They resemble the corresponding structures in 

 Ampliiura more than those of OpJi iopJiragmus. 



5. The radial shields are unusually broad for an Amphiuran, 

 yet not more so than in some recognized species. 



6. The ridge of scales at the margin of the disk, although 

 slight, is Ophiophragman ; but it cannot be of any physiological 

 importance. 



Probably the species should be classified with the genus Opliio- 

 phragmus, although the Amphiuran alliance is evident. 



Ophiophkagmus affixis, sp. nov. (Plate VIII. figs. 4-6.) 



The disk is circular in outline, except where slightly indented 

 over the arms, and it is rather tumid. The scaling is small above, 

 but distinct, and is largest centrally and in the interradial spaces. 

 Primary plates not very conspicuous. On the underside of the 

 disk the scaling is smaller and overlapping. A ridge of minute 

 scales at the interbrachial margins projecting. Eadial shields 

 twice as long as broad, pip-shaped, close and joined except near 

 their inner ends, where a single scale intervenes : a projection 

 on the outer angle. Mouth-shields small, spear-headed, blunt, 

 angular orally, and with a stalk-like process aborally, covered 

 with a thin skin. Side mouth-shields small, covered. 



Jaws broad ; four mouth-papillae on each side — the outer on the 

 side mouth-shield, the two following more or less united, and 

 the innermost below the teeth, but sloping somewhat besides 

 projecting in wards. 



Arms long, 55 times the diameter of the disk in length, slender, 



