OPIIIOTIIRIX SPICULATA. 107 



Opliiothrix spiculata LkContk. 



OpJunlhrir spiriildta J. L. Lr.CoNTK. Pntci-cd. riiil. Acad., X. p. ni.S. 1851. 

 Ojiliiolfirix sjiiculala LiJTKKX. Addit. ad Hist. ()|)Ii., p. 1.">1. l.S.j!). 



Special 3/arks. — Pale col)alt-l)liio in aUrohol ; longest ann-spine.s to 

 under arm-plates as o.l : .0. Disk .soiiietiines as large as 11.5""" ; speci- 

 mens variable. 



Descrij^i'ion of a Specimen. — Diameter of disk, 0""™ ; from outer 

 side of mouth-shield to outer corner of opposite mouth-slit, 4"""'- ; width 

 of arm without spines, 2"'"'" ; length of arm, 51"™" ; distance from outer 

 side of mouth-shield to inner points of tooth-papilla}, to that between 

 outer corners of mouth-slits, 2 : 2. Tooth-papillaa, lowermost ones 

 rounded, small, stout, making a cluster of about twelve ; between this 

 cluster and the teeth there are six very large, stout papilla} arranged 

 in pairs. Teeth five, llattened, squarish, with rounded edge unusually 

 stout and thick ; uppermost one smaller and more tapering. Moutli- 

 shields broader than long, with a slight peak inward ; without, rounded ; 

 length to breadth, .8 : 1.4. Side mouth-shields meeting within. Under 

 arm-plates broader than long, inner side shorter than outer, outer side 

 a little re-enteringly carved, inner side nearly straight, lateral sides 

 irregularly curved, outer corners strongly rounded ; length to breadth 

 (eleventh plate), .6:1; first four or five plates smaller and more square. 

 Upper arm-plates with a median ridge, diamond-shape, with lateral cor- 

 ners acute, outer corners rounded, and inner corner truncated ; length 

 to breadth (third plate), .6 : 1. Brachial and interbrachial rays of disk 

 closely beset with small and large spines, the small being usually about 

 ^mm. \qy^^^ surmounted by a crown of from three to six thorns, and some- 

 times with one or two thorns on their sides ; the large ones are some- 

 times as long as 1.7°""-, similar in shape to arm-spines, but more slender, 

 and bearing from five to eight fine thorns on each edge, and three or four 

 at the tip. In interbrachial spaces below, only a few short, scattered 

 spines ; none at all close to mouth-shields. Radial shields large ; length 

 to breadth, 2.5 : 2 ; though oljscured by the surrounding spines, they 

 are themselves nearly naked, bearing only a few short spines, which 

 are chiefly on the inner angle ; they touch each other with their outer 

 end, which is a little swelled, and has a short, narrow, raised edge. 

 Arm-spines near base of arm, usually seven, rather slender, slightly 

 tapering ; longest ones with from fourteen to twenty-four fine thorns 

 on each edge, and a cluster of still finer ones at the end ; upper spine 

 most tapering ; second one longest, and cut off pretty .'-quare at the 

 end, as are also the third and fourth spines ; second spine often has a 



