MUSEUM OF COMPARATIVE ZOOLOGY. 321 



interbrachial species, below. A row of papillae along the outer end of the 

 radial shield and the edge of the disk. Two arm-spines. 



Description of a Specimen. — Diameter of disk 8 mm. Length of arm 

 (broken) about 50 mm. Mouth-papilla; seventeen to twenty-one to each 

 angle: of these, usually three are rounded, tapering, spear-head shape, and 

 point to the centre of the mouth, being placed at the apex of the angle ; 

 the remainder are much smaller, and are flat and squarish ; they form a 

 connected row, the two outermost usually borne on the edge of the side 

 mouth-shield, the remainder on the mouth-frames. Teeth, four ; flat, deli- 

 cate, long, and tapering to a point. Mouth-shields broad, rounded heart- 

 shape, with a little peak within. Side mouth-shields long and narrow; 

 they begin at the junction of the first under arm-plate with the side arm- 

 plate of the second joint, and run thence across the end of the genital slit, 

 meeting nearly, or quite, at the inner point of the mouth-shield. Under 

 arm-plates in contact with each other along the whole basal part of the arm. 

 First plate small, round hexagonal, longer than broad, and wedged between 

 the outer ends of the neighboring side mouth-shields. Second plate nar- 

 rowed within, and bounded by six sides; as follows: outer side nearly 

 straight ; laterals short and straight ; inner laterals re-enteringiy curved, to 

 admit the large tentacle pores, and converging on the inner side, which is 

 straight and very short. Fifth plate as broad as long; outer side slightly 

 re-enteringly curved ; inner side a little curved ; laterals nearly straight, 

 inner laterals short, and a little re-enteringly curved ; length to breadth 

 .6 : .6. Two thirds out on the arm, the side arm-plates meet below, along 

 a line about one-half as long as the under arm-plate, which is there tri- 

 angular, with its sides a little curved, and the apex directed inward. Side 

 arm-plates robust, but not meeting below or above till near the end of the 

 arm. Upper arm-plates four-sided, broader than long ; outer side curved ; 

 inner side re-enteringly curved; laterals straight; length to breadth (4th 

 plate) .6 : .8. The first upper arm-plate is very small, and fits in the little 

 notch made by the outer ends of the radial shields. Two thirds out on the 

 arm the plates have the same form, though much more elongated. Disk 

 covered, above and below, with numerous rather large plates of very 

 irregular outline, all of which, except those of the lower surface, are more 

 or less studded with small, smooth granules ; on the under surface is an 

 irregular double row of granules, extending round the inner end of the 

 genital slit, and along the genital plates as far as the third joint of the arm : 

 a row of large granules, or short, stout papillae, runs along the edge of the 



basal upper arm-plates ; the ann-eomb of papillae is continued along the edge of the disk ; 

 the side arm plates do not join below; the first pair of pores of the arm-tentacles are sur- 

 rounded by scales. Nevertheless, I am not clear enough as to the generic differences in 

 this group to make a separation. 

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