﻿OPIIIOPLOCUS IMI5RICATUS. 69 



OpMoplocus imbricatus Lyman. 



Opldolepis imhricata Mull. & Tnoscn. System dor Asteridcn, p. 93. 

 Opiuoplocus tessellatus Lyman. Proc. Boston Soc. Nat. Hist., VIll. p. 7G. 18G1. 



Special Harks. — Color gray, with oljscure cross-bands on the arms ; 

 length of arms, in adults, four to five and a half times the diameter of 

 the disk. 



Descrqjtion of a Specimen. — Diameter of disk, 17°"° ; width of arm 

 without spines, o.S"""" ; length of arm, TO""- ; mouth-pap illaj, five on 

 each side, and one odd one, placed just under the teeth ; the side 

 papillaj squarish, flat, and crowded, the odd one resembling the teeth. 

 Teeth five, thick, short, stout, broader than long, with a curved cutting 

 edge. Mouth-shields broad heart-shape, with a curve without and an 

 angle within ; length to breadth, 1 : 1.5. Side mouth-shields large, and 

 of even width, .5°"°- wide. Under arm-plates squarish, very regular and 

 clear in outline, slightly separated, thick ; outer side curved, lateral 

 sides a little re-enteringly curved ; length to breadth (tenth plate), 

 1 : 1.3. The halves of the upper arm-plates are rounded triangular, 

 very much like the su23plemeiitary pieces in Opliionereis ; at the base 

 of the arm they lie very low down, so that the side arm-plates are 

 much reduced in size ; they are separated from each other by six sup- 

 plementary pieces, of which one lies on the middle line of the arm, 

 and the other five make a sort of semicircle round it ; at the base of 

 the arm the central piece of this semicircle becomes very small indeed, 

 and is often divided in two ; between the supplementary pieces there 

 are sometimes single large grains. The halves of the upper arm-plates 

 and the supplementary pieces are thick and swelled, and often of about 

 the same size. Side arm-plates small, and almost covered up by the 

 arm-spines. Scales of the disk a little larger above than below, mostly 

 overlapping, but with here and there a round scale, varying somewhat 

 in size, the largest .8°"°' long. Radial shields very small, about 1"" long, 

 sunken in the scaling of the disk. Genital slits only 2°"° long, starting 

 1°""- outside the mouth-shield. Arm-spines three, stout, round, blunt ; 

 the lowest much the largest ; lengths to that of under arm-plate, .8, 1, 

 1.3 : 1. Tentacle-scales two, longer than broad, flat, nearly oval. Color, 

 in alcohol: gray, with very obscure cross-bars of darker on the arms. 

 According to a colored sketch by Mr. Garrett, the tints of the livmg 

 animal are about the same. 



Variations. — The characters of fifteen specimens which I have 

 examined were very uniform, only the young have shorter arms. 

 The proportions of the disk to the arms in specimens of different sizes 



