Ol'lllONEliElS KETICULATA. 141 



Ophionereis reticulata Litken. 



Ophiurn rt'.icidatn Say. Ji)iini. I'liil. Acad., V. p. 148. 1825. 

 Op/iloU'pis nereis LiJTKKX. \'i(k'nsk. Mi'ddclclscr. March, 1856. 

 Ophionereis reticulata LuTKEX. Addit. ad Hist. Opli., p. 110. 



Special JI((r/,'x. — Disk yellowish brown, with a network of live 

 l)rowii lines. Middle arm-spine about twice as long as the under arm- 

 plate. 



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

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

 Avidth of arm without spines, 2.2"""" ; length of arm, 90""""; distance 

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

 between outer corners of mouth-slits, as 2 : 2.2, Ten moutli-});n)ill;i! to 

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

 Hat, and stout ; the two innermost ones point to centre of mouth, and 

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

 lowest one smallest. Mouth-shields long heart-shaped, 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 little re-enteringly curved, outer corners well rounded, 

 inner corners slightly peaked ; length to breadth, .8:1; 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 tlian broad. 

 Side arm-plates small, being reduced to a ridge, bearing arm-spines ; 

 this is very low, so that leases 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 Ojihiocoma crcissispina), 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 sliape ; twelfth plate larger ; length to breadth, .8 : 1.6 ; 

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

 curve, Init quite distinct ; length to breadth, .0 : 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 



