404 THE VOYAGE OF ILM.S. CHALLENGER. 



4. Ophidiastcr tuberifer, n. sp. (PI. LXV. figs. 1-4). 



Pays five. E = 48 mm. ; r = 7 mm. E < 7r. Breadth of a ray near the base, 8 mm., 

 and 5 mm. broad at about 7 or 8 mm. from the extremity. 



Rays elongate, cylindrical, tapering slightly towards the tip, which is rather obtuse. 

 Disk small, slightly convex. Interbrachial arcs subacute. 



The abactinal and marginal plates, which are arranged with great regularity in seven 

 longitudinal series, are small and slightly convex, and united by well-defined, slightly 

 raised dissepiments. The plates and dissepiments are covered with rather large, rounded 

 granules, those on the median region of the plate usually larger. Many of the plates bear 

 a single, comparatively large, robust, conical, smooth tubercle, and on the outer part of the 

 ray all the plates may be thus furnished, excepting the series on each side of the median 

 radial line of plates. Small entrenched pedicellarise of the characteristic figure-of-eight 

 form, named by Perrier 1 " pedicellaires en saliere," are frequent near the margin of the 

 plates adjacent to a papular area, but there is much variation in different specimens 

 as to the number of pedicellarise present ; and the same remark applies to the conical 

 tubercles ; on one example scarcely any tubercles are present. 



The papular areas, which are very regular, and subcircular or slightly oval in outline, 

 form six longitudinal series. They are slightly depressed, which gives great prominence 

 to the plates and dissepiments, and are covered with small rounded granules, smaller than 

 those on the plates ; there are about ten to twelve papulse in each, and occasionally more. 



The actinal intermediate plates are covered with large, uniform, rounded granules, 

 larger than those of the marginal plates, the whole so uniform and crowded that it is 

 almost impossible to distinguish the separate plates. 



The armature of the adambulacral plates appears to form three series, at least on the 

 inner part of the ray. Of the inner or furrow spines there are two to each plate, and 

 these form a continuous series along the furrow ; they are short, obtuse, compressed 

 laterally, and each alternate spinelet is rather larger than its companion. Immediately 

 behind the furrow series is a single and rather shorter spinelet or papilliform granule, not 

 quite midway between the large and small furrow sj^ines, but rather nearer the former. 

 Behind these and opposite the larger furrow spinelet is a robust fusiform spinelet, which 

 forms an outer series similar to that found in Ophidiaster generally. In the interspaces 

 between these spines small miliary granules are present, which extend up to the furrow 

 series, and thus separate the spinelets or papillae of the median series also. 



Entrenched pedicellarise simdar to those on the abactinal area are present on the 

 actinal intermediate plates immediately behind the large outer spines on the adambulacral 

 plates. Sometimes a short series, fairly equidistantly spaced, occurs, but often only 

 isolated ones are present. The number varies in different examples. 



The madreporiform body, which is rather large and subcircular, is situated near the 

 1 R6vis. Stell. Mus., p. 125 (Archives de Zool. exper., 1875, t. iv. p. 389). 



