REPORT ON THE ECHINOIDEA. 193 



detailed examination of the smaller S23ecimens for those more important regions, and 

 have added such structural features from the larger specimen as could be detected with- 

 out injuring it. 



The test of the larger specimen is comparatively stout ; the abactinal region is covered 

 posteriorly to the peripetalous fascicle with slender slightly club-shaped spines of uniform 

 length (PL XXXIII. fig. 1) ; witliin the peripetalous fascicle the spines are longer, not 

 club-shaped, somewhat more slender, and less crowded together (PL XXXIII. figs. 1, 3). 

 Towards the ambitus the spines are somewhat more crowded (PL XXXIII. fig. 3), and on 

 the actinal side they are club-shaped, longer, stouter, and closely packed round the 

 exterior half of the actinal region (PL XXXIII. fig. 2). The median space is left quite 

 bare towards the small actinal plastron and round the actinostome ; the actinal plastron 

 carries a small number of large spathiform curved spines. 



The test is quite cylindrical (PL XXXIII. figs. 5,5'), and the anal system (PL XXXIII. 

 figs. 1, 5, 7) is placed well up on the abactinal surface. Seen in profile (PL XXXIII. 

 fig. 3), the anterior part of the test is abruptly rounded, curving more gradually 

 towards the apex, which is posterior to the apical system and placed somewhat anteriorly 

 immediately beyond the broad peripetalous fascicle (PL XXXIII. figs. 3, 5') ; it then 

 curves more gradually towards the posterior extremity which is pointed. 



Seen from above, the outline is rounded anteriorly (PL XXXIII. figs. 1, 2), with a 

 slight re-entering angle at the odd median ambulacral area. Even in this largest 

 specimen the gigantic ambulacral suckers (PL XXXIII. fig. 1) of the odd anterior 

 ambulacrum, usually characteristic in Spataugoids of tlie younger stages only, are fully as 

 prominent as in the smaller specimen (PL XXXIII. figs. 8, 10). There are eight of these 

 gigantic ambulacral feet surmounted with huge sucking disks (PL XXXIII, figs. 1, 5', G, 

 8, 10) ; through the genital openings pass four long slender pointed tubes (PL XXXIII. 

 figs. 5, 6, 8). These large ambulacral feet are placed on each side of a broad median 

 amljulacral zone (PL XXXIII. figs. 5, 6, 8) ; the principal jaeripetalous fascicle is very 

 broad near the apex, rounded posteriorly (PL XXXIII. fig. 1), and gradually slopes 

 towards the ambitus on the anterior part of the test (PL XXXIII. fig. 3 ; PL XXXIII.'' 

 fig. 9). The actinostome is cii'cular, placed in advance of the centre (PL XXXIII. fig. 2 ; 

 PL XXXIII." figs. 8, 11), surrounded by a ring of ten large ambulacral suckers (figured by 

 Thomson, Voyage of the Challenger, vol. i. p. 381, fig. 99). The genital organs form 

 flattened clusters occupying the anterior abactinal part of the test (PL XXXIII. fig. 4). 

 The intestinal canal runs at first towards the anal part of the test (PL XXXIII. fig. 4), 

 thence it makes a complete loop to the anterior end, back again to the posterior extremity 

 and then runs again towards the anterior edge of the test, enclosing at the posterior end 

 the first part of the alimentary canal which starts from the actinostome. From tlie 

 second anterior loop it runs to the posterior part of the test, forming a small loop again, 

 before the small intestine finally passes to the anal opening. 



(ZOOL. CHALI,. EXP. PAKT IX. — 18t?l) I 25 



