DESCRIPTIONS OF NEW GENERA AND SPECIES. 



Ophiomusmm acuferum sp. uov. 



Plate I. f. 1-5. 



Special Marks. — A supplementary arm-spine on the upper surface of the 

 side arm-plate. A few large grains on the back of the disk. The margin of 

 the interbrachial space formed by a swelled plate having a deep indentation. 



Description of an Individual. — Diameter of disk, 7™°'. Width of arm with- 

 out spines, 2°"°-. Length of arm about 15°"°'. Mouth-papillae four on each 

 side, and one diamond-shaped, at the apex of the jaw ; all forming a continuous 

 line, as is usual in the genus. The mouth-frames and jaws seen from the side 

 {Fig. jf) have a humpy, shapeless look, and bear at their apex a small jaw- 

 plate which carries two or three small spiniform teeth. Mouth-shields large, 

 five-sided, with a long acute angle within, whereof a part is bounded by the 

 inner ends of the genital openings ; length to breadth, 1.4 : 1.3. Side mouth- 

 shields long triangular, with variously curved sides ; they scarcely meet 

 within, and are partly separated from the mouth-shield by the inner ends of 

 the genital openings. There are only two under arm-plates of conspicuous 

 size : these are the second and third, which are pentagonal, with an angle 

 inward, and lateral and inner lateral sides re-enteringly curved ; length to 

 breadth (3d plate), .8 : .8. Beyond, the under arm-plates are minute trian- 

 gular scales just at the angle of junction of the side arm-plates. These 

 last are thick, swollen, meeting broadly above and below, and composing the 

 almost entire covering of the arm on the part beyond the disk. Near the 

 tip of the arm {Fig. S) there is neither upper nor under plate, and the joints 

 are elongated and larger at their outer end. Upper arm-plates minute, trian- 

 gular, with an angle inward ; length to breadth, on joints near the disk, .4 : .7. 

 Disk covered with plates, of which some are unusually thick and swollen ; 

 the central space inside the radial shields is set with flat angular plates, 



