CLARK: OPHU'KOIDEA. 443 



the distalniost largest. Tooth-papillae only ii-o on each jaw tip. 

 Under arm-plates tetragonal with slightly rounded corners, longer 

 than wide, little or not at all in contact. . Side arm-plates moderately 

 large, meeting below; each carries 2 or 3 prominent spines; when 3 

 are present, the uppermost is largest and is often very large, its length 

 equalling 2-3 arm-segments and its thickness proportionately great; 

 near the middle of the arm, segments with two or with three spines 

 alternate with considerable regularity; the big uppermost spines 

 occur at intervals of 2-5 segments and alternate on the two sides of 

 the arm. Tentacle-scale single, small and rounded. Color (dried): — 

 disk dull light olive with a very few lighter markings; disk-spines 

 dull yellowish; upper arm-plates dull olive l)ut at intervals of 4-6 

 segments, the upper arm-plate is dull cream-color; upper half of side 

 arm-plates and uppermost spines, usually dull olive but when upper 

 arm-plate is cream-color the adjoining side arm-plate and the upper- 

 most spine it carries is usually the same; lower surface of disk and 

 arms, including smaller arm-spines very pale browm; some arm- 

 spines more or less distinctly annulated with dusky or olive. 



Paumotu Islands: Makemo. 



One specimen. 



Although this specimen is obviously immature, it differs so much 

 from previously known members of the genus, it is necessary to 

 designate it by a new name. The name given is based on one of the 

 striking features, the presence of only two arm-spines on many of the 

 side arm-plates. This character taken in connection with the disk- 

 covering, the upper arm-plates and the coloration will serve to dis- 

 tinguish the species at once from all other members of the genus. 



Ophiodermatidae . 



Ophioderma panamense. 

 Lutken, 1859. Add. ad hist. Oph., pt. 2, p. 91. 

 Two specimens from Perico Island, Panama, call for no comment. 



Ophioderma pentacantha,^ sp. nov. 



Plate 3; Plate 4, fig. 1, 2. 



Disk, 27 mm. in diameter; arms 14o-150 mm. long. Disk covered 

 with the usual coat of coarse, overlapped scales, completely con- 



' TTtVTi = five + aKauBoL — a spino, in reference? to I hi' live arm-spines. 



