340 BULLETIN OF THE 



Despite the number of Amphiurce described from the Gulf of Mexico 

 and waters of Brazil, the species seem well defined and distinct ; and 

 there is promise of many more. This genus is remarkable fort he well- 

 defined specific differences it presents in the character and position of its 

 side mouth-shields, arm-plates, mouth-papilhe, radial shields, &c. For 

 example, no other Amphiura presents the following combination found in 

 A. pulchella : 1. Three mouth-papilla? on a side, the innermost thick- 

 ened. 2. Slender radial shields, closely joined. 3. Upper and lower arm- 

 plates separated. 4. Three arm-spines. 5. One tentacle scale. 



Ophiocnida olivacea Lyman, sp. nov. 



Spcciul Marks. — Radical shields deeply sunk in the disk, long and 

 narrow. Disk puffy, with a narrow notch over each arm. At the base of 

 the arm two tentacle scales, of which one is small and stands on the side 

 arm-plate, the other long spiniform and borne on the lateral side of the 

 under arm-plate. 



Description of a Specimen. — Diameter of disk 12 mm. Length of arm 

 about 85 mm. Mouth-papilla?, twelve to each angle, arranged in three 

 sets : first, two small, flat, tooth-like papillae, one at each outer corner of 

 the mouth-slit, standing well above the outer end of the side mouth-shield 

 (these, of course, are the tentacle scales of the mouth-tentacles) ; secondly, 

 four sharp, stout, rounded, tapering papilla? on each side, standing in a row, 

 which runs from the middle point of the side mouth-shield, upwards and 

 inwards, along the mouth-frames to a level with the second tooth ; of these 

 the outer one is largest, .7 mm. long; thirdly, two stout, conical papilla? 

 standing on the point of the mouth-frames, and directed inward, but inclined 

 from each other, so that they have the appearance of a blunt fork. Teeth 

 six, of which the lowest is pointed somewhat like the mouth-papilla? next 

 to it ; the other five are flat, squarish, with a curved cutting edge. Mouth- 

 shields small, of a broad, rounded heart-shape ; length to breadth 1.4 : .7. 

 Side mouth-shields narrow and small, pointed within (where they nearly 

 meet), broader without, where they run to the lateral corner of the mouth- 

 shield. Under arm-plates longer than broad, bounded within by a nearly 

 straight line, on the sides by re-entering curves, and without by two little re- 

 entering curves, which join in a small peak on the median line ; length to 

 breadth (10th joint) .8 : .G. Inside the disk these plates are especially en- 

 croached on by the tentacles, which are very large, and occupy much of the 

 under surface of the arm. Side arm-plates moderately prominent, and con- 

 spicuous from below by reason of the narrow under arm-plates ; they do not, 

 however, meet, except at the very tip of the arm, where they come together 

 above. Upper arm-plates broader than long, a little broader without than 

 within ; all their sides nearly straight; the outer one lightly curved ; length 



