PROCEEDINGS OF THE NATIONAL MUSEUM. 291 



ezoidal or pentagonal plate adjoining the distal end of the mouth- 

 shield, by two large, elongated genital plates, and by a submarginal 

 row of about three or four angular plates, of which one or two, in the 

 middle, are much smaller than the rest. 



The mouth-shields are large, pentagonal, rather longer than broad, 

 the length in the larger specimens being about 3.5 mm. and the breadth 

 about 3 mm.; the distal margin is straight, or somewhat incurved; the 

 lateral margins nearly parallel, and the inner edges are nearly straight, 

 meeting nearly at a right angle. The side mouth-shields are narrow 

 and oblong, with nearly parallel sides. The genital papiliie commence 

 at the mouth-shields as a single row of small irregular granules, but 

 become more numerous distally, and at the edge of the disk, near the 

 base of the arms, form an elongated, triangulai- group of rather large, 

 unequal granules, about twelve to fifteen in number. 



The teeth are short, stout, angular, and blunt. The niouth-papillte, 

 in specimens 10 to 13 mm. in diameter, form a nearly regular close row 

 of six to eight; they are small, short, blunt, flattened, and usually 

 squarish in outline, though some are oblong, and twice as broad as 

 high; toward the distal end of the mouth-slits more or less of the 

 papilhe are often soldered together. In the largest specimens the 

 mouth papilliie become more irregular and often form two rows, besides 

 a row of granules above them; those of the lower row are stout, blunt, 

 conical, unequal in size; those of the upper series are much smaller, 

 rounded or conical. 



The inner tentacle-pores, in the large specimens, are bordered by six 

 or seven short, blunt, squarish scales on each side; the second pair has 

 three or four very small scales on each side; the third, about three 

 minute scales on each side; and the fourth pair has two on the proxi- 

 mal, and one, more minute, ou the distal side ; beyond the fourth pair 

 of pores, which are minute, no pores are visible, though a distinct pit 

 exists, bordered by a single minute spiniform tentacle-scale oii the 

 proximal side, and by the lower arm sjMne. 



The arm spines are usually three, very minute, and nearly equal; the 

 ui))»erraost is near the upper distal angle of the side arm-plate and 

 widely separated from the others; the lowest is usually close to, or in 

 contact with, the tentacle scale; the arm-spines are not more than one- 

 fifth or one- sixth the length of the side arm-plates. 



The dorsal arm-plates are thickciied, but not much swollen, and are 

 separated by rather wide and deep grooves ; the two or three basal 

 ones in the notch of the disk are short and small; the first free plate 

 is shorter than broad, somewhat lunate; the plates succeeding this 

 become constantly longer in proportion to their breadth; for a short 

 distance from the base of the arms they are trapezoidal and have a 

 strongly curved outer margin, straight convergent sides, and a narrow 

 incurved proximal margin; beyond the middle of the arm they become 

 triangular or wedge shaped with the distal margin strongly convex 



