MUSEUM OF COMPARATIVE ZOOLOGY. 317 



large as any ; broader than long; of a rounded diamond-shape, with a dis- 

 tinct, rounded peak without; length to breadth .C : .9. Second plate 

 touching the first ; third plate barely separated from the second by the 

 juncture of the under arm-plates ; fourtli plate well separated from its suc- 

 cessor, as are all those beyond. Fifth plate bounded within by two re- 

 entering curves, which come to a point on the median line ; without, it has 

 a little peak in the centre which gives it a faintly tri-lobed appearance ; 

 the laterals are short and straight ; length to breadth .5 : .8. The plates 

 beyond this one have a similar form, but continually grow smaller by the 

 increased encroachment of the side arm-plates. Side arm-plates meet be- 

 low at the third under arm-plate ; and, above, at the ninth upper arm-plate : 

 their upper edges are re-enteringly curved, which gives a peculiar shape to 

 the upper arm-plates. These last are, near the disk, broader without than 

 within, with a strongly curved and thickened outer side ; and their laterals 

 are curved by reason of the peculiar form of the side-plates ; further out, 

 where they do not touch each other, they come to a point, within ; length to 

 breadth (sixth plate) .8 : .7. Disk, above, covered with crowded, irregular, 

 flattened scales, none of which are much swelled, so that the surface is nearly 

 smooth. The primary plates are not conspicuous either by size or thick- 

 ness, except the central one, which is very distinct, nearly round, and .6 

 mm. in diameter. Radial shields large, thick, and conspicuous ; irregular 

 pear-seed shape, and strongly diverging; length to breadth 2 : 1.4; they 

 are entirely separated by a very irregular wedge of scales, which some- 

 times consists of a double row ; sometimes of a mixture of a single and 

 double row, respectively of larger and smaller scales. The large, thick 

 radial-scales carry all the papilla; of the arm-comb, which are about twenty 

 in number on each side and of two sorts ; those seen from above are sharp 

 and diverge from each other ; those seen from below are flat and square, 

 so as to form an even, close-set row; there are about ten of each kind, and 

 those at the ends of the row differ most. The arm-comb is continued, along 

 the edge of the genital slit, by a row of about seventeen very fine papilla;. 

 On the upper arm-plates within the notch is a row of fine papilla; corre- 

 sponding to those of the arm-comb. The scales of the interbrachial spaces 

 below are thin and crowded. Arm-spines cylindrical, blunt, scarcely ta- 

 pering; lengths to that of the under arm-plate (eighth joint) .4, .2, .3 : .5. 

 Further out on the arm they are proportionately much longer, and towards 

 the last third of the length the lowest spine is nearly or quite as long as 

 the side arm-plate ; there, also, they are more slender, and taper to a fine 

 point. Twelve tentacle scales on the first pore, seven being on the side 

 next the interbrachial space ; six scales on the second pore ; five on the 

 third ; four on the fourth ; three on the fifth ; two on the sixth ; and one 

 scale on the joints beyond that. 



