48 



OPIIIOGLYPIIA LUTKENII. 



shaped, with an angle turned inward, and outer side rounded ; lateral 

 corners somewhat projecting ; length to breadth, 3 : 3. Side mouth- 

 shields straight, narrow, tapering, meeting within. Under arm-plates, 

 at base of arm, broad, triangular, with lateral corners somewhat 

 rounded ; length to breadth, 1 : 2.5 ; farther out on arm, the plates, as 

 is usual in the genus, grow smaller and smaller, from being encroached 

 on by the side arm-plates. Upper arm-plates much broader than long, 

 and having the outer and inner sides straight and ^^arallel, and nearly 

 equal ; outer corners rounded ; length to l^readth near base of arm, 

 1.2 : 3.5. Scales of disk, above and below, not arched or swelled, but 

 lying very flat and evenly ; primary plates rounded, and conspicuous 

 by their size. Kadial shields broad, pentagonal, with outer angles 

 rounded, and a sharp angle directed inward ; completely separated by 

 the mnermost upper arm-plates ; length to breadth, 2.8 : 2. Notches in 

 disk, at base of arms, deep, admitting fully four arm-plates. Comb on 

 the edges of each notch made up of thick, flat, spreading papilla?, 

 crowded side by side, in a continuous line. These papillae are only six 

 or seven ; they decrease in length as they pass under the disk, where 

 they join the narrow, toothed edge that runs along the margin of each 

 genital slit. On base of arm proper, no comb, or line of papilla?. Arm- 

 spines three, tapering, sharp ; upper one longest, and equal to about 

 one and a half joints ; lowest one shortest, and equal to a little less 

 than one joint. Tentacle-scales of innermost pair of pores short, stout, 

 crowded, flattened ; usually four or five on the outer side, and four, 

 somewhat smaller, on the inner side of each pore. Rest of tentacles 

 with only one round and rather thick scale, but there may also l)e a 

 little tooth, just outside the tentacle. Color, in alcohol : above, bluish 

 gray (a sort of clay color), with darker markings ; the arms the same, 

 with darker bands ; below, arms whitish ; interbrachial spaces of a pur- 

 plish hue, with white spots. 



This species is nearest 0. Sarsii, but differs in the want of a row of 

 papilla? on the base of the arm, above ; in having the papilla? of the 

 arm-comb and of the inner pair of tentacle-pores more crowded and 

 blunter ; in the finer and sharper mouth-pajDillce, &c. 



LIST OF SPECIMENS. 



