REPORT ON THE OPHIUROIDEA. 33 



Station 78.— July 10, 1873; lat. 37° 24' N., long. 25" 13' W. ; 1000 fatlioms ; 

 globigerina ooze. Station 1 46.— December 29, 1873; lat. 46° 46' S., long. 45° 31' 

 E; 1375 fathoms; globigerina ooze. Station 156.— Februaiy 26, 1874; lat. 62° 26' 

 S., long. 95°44'E. ; 1975 fathoms ; diatom ooze. 



OpMopyrgus. 

 OpMopyrgiis, Lym., Bull. Miis. Comp. ZooL, vol. v. part 7, 1878. 



Disk high and dome-shaped, covered with thick swollen plates, and surmounted by a 

 central primary plate, which rises like a cone. Ai-ms slender, smooth, and tul^ular, with 

 side arm plates very large, and upper and under arm plates small. Basal tentacle pores 

 very large ; those beyond small and situated near sides of arm. An arm comb. Arm 

 spines minute, and standing on outer edge of side arm plate. Two long genital openings 

 in each interbrachial space. 



This is the most singular-looking genus yet found among the Ophiuridse. With its peg- 

 like central primary plate and dome-like disk it suggests a simple armed Crinoid whose 

 head has been broken from the stem. By its heavy, closely soldered plates and peculiar 

 tentacle pores, it recalls OiMomusium ; by its enclosed mouth tentacles and arm comb, 

 it brings to mind the deep-sea Ophioglyjihce, but it differs pretty widely from both. 



Opliiopyrgus ivyville-thomsoni, Lym. (PI. IX. figs. 15-17). 



Ophiopyrgus imjville-ihomsoni, Lym., Bull. Mus. Comp. ZooL, vol. v., part 7, p. 121, pi. v. figs. 

 135-137, 1878. 



One minute arm spine on basal joint ; farther out, none ; a double arm comb over top 

 of arm, the upper one consistijig of three or four small papillse on edge of outer end of 

 genital scale ; the under, likewise of three or four papilla?, on edge of side arm plate. 

 Interbrachial space below wlioUy filled by mouth shield. 



Diameter of disk 4 mm; height of disk 4-3 mm; length of arm 13 mm.; width 

 of arm 1 -2 mm. Mouth papillse small, similar, separated, tooth-like ; seven or nine to 

 each angle, whereof the innermost is slightly largest. Mouth shields longer than broad, 

 oval, with a peak inward, occupying the entire interbrachial space below, and bending 

 upwards to half the height of arm. Side mouth shields very small and sunken, meeting 

 within, and covering only the inner peak of mouth shields. First under arm plate very 

 long axe-shape, with a curved edge outward and a long, tapering point inward, compressed 

 between two large oval tentacle pores ; second plate similar, but smaller ; third and fourth 

 plates shorter and still smaller ; beyond which the plates are represented by a small knot 

 of a transverse diamond-shape, and growing rapidly less towards end of arm. Side arm 

 plates large, but not swoUen, meeting widely above and below, occupying most of the arm, 

 which acquires thereby a tubular, rapidly tapering form. The side arm plates belonging 

 to second under plate are wide, and stretch laterally to meet the mouth shield. Disk as 



(zOOL. CHALL. EXP. — PABT XIV. — 1882.) 5 



