OPIIIOTHKIX DUMOSA. 



169 



LIST OF SPECIMENS. 



Ophiothrix dumosa Lymax. 



Opldothrix dumosa Lyma.v. Proceed. Boston Soc. Nat. Hist., \1I. p. 252. 18G0. 



Special 3Iarks. — Upper arm-spine longest. Spines on disk of sev- 

 eral sizes ; stout. Color dull blue. 



Desct^ijjfion of a Specimen. — Diameter of disk, 11. S""' ; from outer 

 side of mouth-shield to outer corner of opposite mouth-slit, 5""°* ; 

 width of arm without spines, 2.2°"°- ; length of arm, 72'"'"- ; distance 

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

 that Ijetween outer corners of mouth-slits, 2.5 : 2.5. Teeth six, squarish, 

 thick ; cutting edge a little rounded, sometimes split in two ; upper one 

 rather narrower and more tapering. Tooth-papilla? aljout thirt^'-eight, 

 arranged in two diverging, principal rows, between which are included 

 some smaller ones ; the.se two rows start, just below the teeth, with 

 a pair of large, flat papilla?, like a tooth split in two ; these are followed 

 by a similar pair, after which the two rows diverge, growing smaller as 

 they pass lower down, and ending in papilla? no larger than those which 

 serve to fill in the middle space ; in each of these principal rows there 

 are about nine papilla?. The arrangement is the same in 0. spicu- 

 Icita. Mouth-shields oval heart-shaped, with a decided peak directed 

 mward ; length to breadth, 1.3 : 1.8. Side mouth-shields rather nar- 

 rower than is common in the genus, meeting within. Under arm-plates 

 much broader than long, hexagonal, with angles more or less rounded ; 

 first four plates smaller than those beyond, and much more rounded ; 

 most of the plates on the first third of the arm are hexagonal, with 



