MUSEUM OF COMPARATIVE ZOOLOGY. 329 



notch or re-entering angle in cadi interbrachial space. In the centre of 

 the disk, and on the dividing lines between the shields, are a few rough 

 grains or rather thorny stumps, of which each shield bears one or more 

 near its outer end. Interbrachial space below wholly occupied by the 

 very stout and swollen side mouth-shields, and the mouth-shield which 

 closely fills the angle made by them. Under arm-plates bounded without 

 by a curve, on the sides by re-entering curves, and within by an angle. 

 Side mouth-shields stout and meeting above and below. Upper arm-plates 

 fan-shape, with a curve without and a sharp angle within. Arm-spines 

 (2d joint from disk) six ; the three upper ones shaped as in the adult ; the 

 three lower much shorter and stouter, and suddenly swollen at the base ; 

 on the joints just beyond, five spines, which are short and stout. The 

 chewing apparatus and other characters are nearly as in the specimen first 

 described. It will be seen that, in character of arm-spines, armature of 

 disk, and proportionate length of arm, this specimen differs much from its 

 supposed adult ; but I shall consider it as the young form, unless interme- 

 diate stages shall prove it a distinct species. 



Both specimens from off Chozera, Cuba, in 270 fathoms. 



This animal has a tendency to roll the tips of the arms upon themselves, 

 which, with the contracted disk and the character of the arm-plates, give 

 it the look of a young Astrophjton. 



Ophiactis humilis Lyman. 



Special Marks. — Disk covered with coarse scales, which are beset with 

 short spines and short thorny club's. Five spines, the two uppermost much 

 the longest. 



Description of a Specimen. — Diameter of disk 4 mm. Length of arm 11 

 mm. Seven long, rough, stout, spine-like tooth-papilla? .2 mm. long, stand- 

 ing well apart ; the innermost one is broader and flattened, and very like 

 the teeth, below which it stands. Three teeth, which are flat, longer than 

 broad, with their cutting edge bluntly pointed. Mouth-shields broad heart- 

 shape, broader than long, curved without, bounded within by two re-enter- 

 ing curves; length to breadth .3 : .5. Side mouth-shields large, extending 

 outward as far as the outer corner of the mouth-shields ; and loosely joined 

 within, along a line equal nearly to the length of the mouth-shield itself 

 Underarm-plates broader without than within ; bounded without by a slight 

 curve, within by an obtuse angle, and on the sides by re-entering curves ; 

 length (3d plate) .3 mm. Side arm-plates large, meeting below along a line 

 equal to more than half the length of the lower arm plate ; and above, 

 equal to the whole length of an upper arm-plate. Upper arm-plates thick, 

 but small, only about half as wide as the arm itself; heart-shaped, being 

 curved without and pointed within. Disk covered with coarse, somewhat 

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