OPIIIOCOMA INSULARIA. 89 



Ophiocoma insularia Lyman. 



Ophiocoma insularia Lymax. Proceed. Boston Soc. Nat. Hist., VIII. p. 80. 



Special Marl's. — Lower spines longer than the npper ; arms flat, 

 a])out lour times as long as diameter ol' disk ; under arm-plates regular, 

 and al)()ut as long as broad ; interbrachial spaces below closely granu- 

 lated. 



Description of a Specimen. — Diameter of disk, 30"""- ; width of arm 

 without spines, 4.5"""' ; length of arm, 125""°\ Mouth-papilla^, six on 

 each side ; under the teeth there cannot be said to be any mouth- 

 papilkv, because the tooth-papilla^ which sometimes are as many as 

 twent}', extend downwards and outwards, growing smaller and smaller, 

 till they nearly reach the inner end of the mouth-shield. Teeth four, 

 flat and squarish, npper one smallest. Mouth-shields about as long as 

 broad, much rounded, without straight lines ; length to breadth, 2.8 : 2.5. 

 Side mouth-shields small, triangular, lying entirely on the sides of the 

 mouth-shields. Under arm-plates about as broad as long, bounded with- 

 out by a curve, and within by a short inner side and two inner laterals ; 

 length to breadth (sixteenth plate), 2 : 2. Upper arm-plates even and 

 regular, much broader than long, bounded without by a clean curve, 

 and within by an imier side and two inner laterals ; length to breadth, 

 2 : 4. Granulation of the disk extremely close and fine above and 

 below, and extendino; even to the outer corner of the side mouth- 

 shields ; about 45 to a square mm. Arm-spines rather short, little 

 tapering, blunt, a good deal compressed ; on the first few joints beyond 

 the disk, four, very rarely indeed five ; farther out, three ; they do not 

 alternate three and four, as is seen in many other species ; lengths to 

 that of under arm-plate, 3, 3.1, 3.6, 3.5 : 2. Tentacle-scales two, large 

 and regular, much longer than broad. Color, in alcohol : above, deep 

 umber, almost black ; below, interbrachial spaces the same ; arms a 

 little lighter. 



Variations. — A young specimen, with a disk of 9.5™™, had arms 

 35°"°' long ; the mouth-shields were narrower than in the adult, the 

 color was paler, and the tips of the arms were cross-barred with white. 

 A very large specimen, w^ith a disk 33™™' in diameter, had arms 155™™* 

 long ; the proportion of the ann-spines to the under arm-plate was 3.5, 

 3.5, 3.7, 3.7 : 2 ; the upper spines were greatly flattened, and were cut 

 square off at the end. Some well-grown individuals have cross-bars of 

 light-brown towards the end of the arm. 



12 



