﻿OPIIIONEREIS RETICULATA. 141 



Ophionereis reticulata Lutken. 



Ophiura reticulata Say. Jonrn. Phil. Acad., V. p. 148. 1825. 

 Ophiolepui nei-eis LiJTKV.y. Vidcnsk. Meddelelser. March, 18.5G. 

 Ophionereis reticulata Lutkkn. Addit. ad Hist. Oph., p. 110. 



Special Marks. — Disk yellowish brown, with a network of five ^ 

 brown lines. Middle arm-spine about twice as long as the under arm- 

 plate. 



DescrijJtion of a Specimen. — Diameter of disk, 11.5"""'; outer edge 

 of mouth-shield to outer corner of opposite mouth-slit, 4.4"""- ; greatest 

 width of arm without spines, 2.2""°" ; length of arm, 90""°' ; distance 

 from outer edge of mouth-shield to inner points of tooth-papillae, to that 

 between outer corners of mouth-slits, as 2 : 2.2. Ten moutli-papilla3 to 

 each angle of mouth ; outermost one small and sharp ; the rest short, 

 flat, and stout ; the two innermost ones jooint to centre of mouth, and 

 are shortest and most rounded. Teeth five, flat, square, and thin, the 

 lowest one smallest. Mouth-shields long heartrshaped, point inward, 

 varying somewhat in size ; length to breadth, 1.4 : 1.2 ; madreporic 

 shield broader. Side mouth-shields very long triangular, varying some- 

 what, connecting first under arm-plate with mouth-shield ; length to 

 breadth, .8 : .4. Under arm-plates have general form of squares with 

 rounded corners ; first plate very small, narrowest at inner end ; length 

 to breadth, .4 : .4 ; second plate, inner side nearly straight, outer side 

 curved, lateral sides nearly straight ; length to breadth, .6 : .8 ; twelfth 

 plate, outer side a little re-enteringly curved, inner side slightly curved, 

 lateral sides a Uttle re-enteringly curved, outer corners well rounded, 

 inner corners slightly peaked ; length to breadth, .8 : 1 j this is the 

 typical form ; about two thirds out on arm, length to breadth, .8 : .8 ; 

 at tip of arm, plates long heart-shaped, point inward, longer than broad. 

 Side arm-plates small, laeing reduced to a ridge, l^earing arm-spines ; 

 this is very low, so that bases of arm-spines stand almost directly on 

 arm proper. Upper arm-plates have at base of arm the shape of a 

 pointed, distorted oval ; first three plates very small, like scales (some- 

 what as in Ojjhiocoma crassispina), each larger than its successor ; 

 fourth plate, inner side slightly curved, outer side short, lateral sides 

 long and sloping ; length of plate, .6 ; outer corners much rounded, so 

 that outer side and lateral sides may be said to form one curve ; this is 

 the typical shape ; twelfth plate larger ; length to breadth, .8 : 1.6 ; 

 about two thirds out on arm, outer side and laterals not forming one 

 curve, but quite distinct ; length to breadth, .6 : 1.2. Here the supple- 

 mentary plates become much smaller, and finally disappear close to the 

 tip of the arm ; and, on the other hand, the true upper plates begin to 



