54 THE VOYAGE OF H.M.S. CHALLENGER. 



''Salenia hastigera (PI. IV. figs. 3-17; PI. XXXVIII. fig. 10). 



Salenin liasligera, A. Agassiz, 1879, Proc. Am. Acad., vol xiv. p. 198. 



This species difi'ers from Salenia varispina, A. Agassiz (Revis. Echini, pi. iii. figs. 

 8-14), iu the closer and uniform granulation covering the abactinal system, and the more 

 central position of the genital openings (PL IV. fig. 10). The primary spines are 

 comparatively much longer, some of them equalling four times the diameter of the test 

 (PI. IV. fig. 3). They are more or less cylindrical, varying but little in shape. Though 

 they are usually straight, sometimes considerably curved, they taper very gradually and 

 are covered from the base to the tip with numerous small sharp spines closely arranged 

 in regular rings round the shaft (PL IV. fig. 17). On the longest radicles the smaU 

 spines are frequently worn ofi", the extremity of the shaft showing only a delicate longi- 

 tudinal striation. The primary radioles of the actinal surface are similar to those of 

 Salenia varispina, but, although flattened and with few sharp spines along the margin, 

 are quite slender. The spines of the median interambulacral space and of the ambulacral 

 region are short club-shaped but less variable in outline, and more slender, especially 

 towards the abactinal region, than the corresponding spines of Salenia varispina. The 

 apical system of Salenia hastigera conforms entirely in the arrangement of its plates with 

 that of the normal Salenia, the anal system being surrounded by two of the genital plates 

 and by the subanal plate. 



In young specimens of Salenia varispina the anal system encroaches only upon one 

 of the genital plates, and subsequently in older specimens the position of the anal system 

 does not difi'er in the two species. In none of the specimens of Salenia hastigera 

 examined, even the smallest, do we find any indications of the deep pits along the Lines 

 of sutures of the plates of the abactinal system, such as are so well-marked in young 

 specimens of Salenia varispina. The madreporic body is not more prominent than in 

 the other species of the genus; it consists of only four to six small openings adjoining 

 one of the genital openings (PL IV. fig. 16). The ocular plates are proportionally longer 

 and narrower than in Salenia varispina. The anal system is covered by a number of 

 plates irregularly arranged in two to three concentric rows round the anal opening ; they 

 carry small papillEe. In a younger specimen the plates immediately round the anal 

 opening (PL IV. fig. 12) are triangular, much as the plates covering the whole anal 

 system of Salenia varisp>ina. With this exception and the comparatively larger size of 

 the ten buccal plates of the actinal membrane, the smaller specimens of Salenia hastigera 

 (PL IV. figs. 12, 13) already possessed the characteristic features of the larger specimens. 

 The number of primary tubercles in the interamljulacral area is smaller in this species 

 (PL IV. fig. 15) than in Salenia varispina (PL IV. fig. 1), in the proportion of six to 

 eight ; and in the ambulacral area at the actinostome we find only two or three large 

 tubercles (PL IV. fig. 14), while in Salenia varisioina (PL IV. fig. 2) they form, as in 



