﻿18 



OPHIURA BREVISPINA. 



uniform and lighter. The length of the arms seems to average not more 

 than three or three and a half times the diameter of the disk ; thus, 

 20 : 63, 17 : 53, 16 : 45, 9 : 32. A specimen having a disk of O""- agreed 

 entirely with the largest ones, except that the mouth-shields and arm- 

 plates were a little less angular, and there were only eight arm-spines. 

 Very often some of the naked scales at the base of the arms become so 

 developed as to look like little thickened plates. 



This species may be distinguished from other Ophiura3 with equal 

 spines as follows : — 0. guttata has the upper arm-plates divided in many 

 little pieces, and has arm-spines of a different shape ; O. hrevisjnna has 

 long oval mouth-shields, and the arm-spines much less stout ; O. Januarii 

 has only eight arm-spines, which are long and slender ; 0. variegata has 

 longer arm-spines, and mouth-shields longer than broad. 



LIST OF SPECIMENS. 



Whence obtained. 



1078 

 1081 

 1107 



3Iuseum of Comparalice Zoology. 

 Tortusas, Fla. I Feb. 185G. | T. Lvman. 



St. Thomas, W. I. • • • 



West Indies. | ... 



A. H. Rlise. 



Uni v.Mus. Cop'hagen. | 



Smithsonian Institution. 

 St. Thomas, W. I. 

 St. Thomas, W. I. 

 St. Thomas, W. I. 

 St. Thomas, W. I. 



A. II. Riise. 

 A. H. Riise. 

 A. H. Riise. 

 A. H. Riise. 



Ak-oliolic. 

 Dried. 



Ophiura brevispina S.\t. 



Ophiura brevispina Say. Journ. Phil. Acad. V. 149. 1825. 

 Ophioderma serpens Lutken. Addit. ad Hist. Ojjh. 96. 



Sjjecial 3Iai'ks. — Color usually greenish, sometimes tinged with red- 

 dish ; sides of disk generally concave ; diameter of disk about 12""- ; 

 side mouth-shields naked ; mouth-shields long heart-shaped. 



Description of a Specimen. — Diameter of disk, 10.8°"°-; outer edge of 

 mouth-shield to outer corner of opposite mouth-slit, 4.6""° ; greatest 

 width of arm, without spine, 2.5'""- ; length of arm, 42.4"""- ; distance 

 from outer edge of mouth-shield to inner point of tooth-papilte to 

 that between outer corners of mouth-slits, as 2 : 2.2 ; mouth-papillse, 

 usually sixteen to each angle of mouth ; outermost one small, and often 

 partly concealed ; innermost ones pointing nearly to centre of mouth, 

 spearhead-shaped, and longer and broader than the rest; teeth, five, 

 shaped like a tlat, blunt, spearhead ; lowest one smallest ; mouth- 



