54 CAULOPHACUS SCHULZEI. 



are very unequal (Plate 8, figs. 13-15). Sometimes there are a good many, 

 sometimes but a few, occasionally only one, and not infrequently none at all. 

 When the spines are numerous a spiral arrangement of them can occasionally 

 be made out quite distinctly (Plate 8, figs. 13, 15). 



When the lateral rays are markedly reduced in length, their ends are usually 

 thickened (Plate 8, figs. 12, 14, 18, 22). The terminal thickening is either spiny 

 (Plate 8, fig. 14) or smooth (Plate 8, fig. 12). 



The lateral rays are 250 /x-l.l mm. long, and 25-65 ij. thick at the base. 

 The properly developed long ones taper gradually to the rounded end which 

 is 5-12 IX thick. The ends of the longitudinally reduced and terminally thick- 

 ened lateral rays measure 15-25 n in transverse diameter. In some specimens, 

 as for instance in the small one with 30 mm.-disc, the lateral rays of the hypo- 

 dermal pentactines are slightly shorter than those of the hypogastrals, those 

 of the former sometimes measuring in this specimen 0.9 mm. in length, those of 

 the latter 1 mm. In the other specimens, as for instance in the large one D 

 with 60 mm.-disc, the lateral rays of the hypodermal pentactines are consider- 

 ably longer than those of the hypogastrals, those of the former measuring, in 

 this specimen up to 1 mm., those of the latter only up to 670 m in length. 



The proximal ray is straight or shghtly, often irregularly, curved, and tapers 

 gradually to the blunt or rounded end. The basal part of the proximal ray is 

 smooth for a short distance, then follows a region which usually bears broad 

 and low, conic spines. The number of these spines is variable. Sometimes 

 (Plate 8, figs. 7, 16, 17) there are a good many, sometimes only few (Plate 8, 

 figs. 1, 5), and sometimes none at all (Plate 8, fig. 6). When these spines are 

 numerous, the portion of the proximal ray bearing them is usually more or less 

 thickened. The distal and the middle-part of the ray are generally smooth. 



The proximal ray is 600ju-l.l mm. long, and 30-55 yu thick at the base. 

 The maximum thickness of the spiny part is 1-4, rarely as much as 7 ju greater 

 than the thickness of the base of the ray. 



The difference in the length of the proximal ray of the hypodermal and 

 hypogastral pentactines is similar to, but not so great as, the difference in the 

 length of their lateral rays. In the small 30 mm.-disc specimen B the proximal 

 ray of the hypodermals is not over 0.95 mm. long, that of the hypogastrals not 

 over 1.1 mm. In the larger 60 mm.-disc specimen D the proximal ray of the 

 hypodermals is not over 1.1 mm. long, that of the hypogastrals not over 0.96 mm. 



Also in the specimens examined by Wilson {loc. cit., p. 46) the hypodermal 

 and the hypogastral pentactines were very similar. Wilson {loc. cit., p. 46, 47) 



