FOSSIL CRINOIDS. 119 



DiMEROCRINUS SPINIFERUS, sp. IIOV. 



Plate III, figis. lla-d. 



Calyx elongate with straight sides, truncate above and below like the frus- 

 trum of an inverted pyramid; rather wider than high, widest just above the 

 arm bases, enlarging from base to arm facets as 1 to 1.8; IBB and lower part of 

 BB included in lower plane. Dimensions of the only specimen: height 17.5 

 mm.; width at base, 10 mm., at arm bases, 18.5 mm. Base broad and flat; 

 IBB of good size, horizontal, projecting well beyond the column, with tips 

 bending up; BB three times as wide and twice as high as IBB — the largest 

 plates in the calyx — the lower central part produced into spiny nodes, about 

 on a level with the infrabasals; smaller spines form a low ridge leading from 

 these to the middle of the radials. RR a little wider than BB, but only two 

 thirds as high, surmounted by a small spine ; followed by two narrow IBr (ab- 

 normally three in one ray) one fourth the size of the radials, also spiniferous; 

 and these by one very large, overhanging, spiniferous IIBr at each side, bearing 

 the arm facets; between these a large, wedge-shaped, tumid plate, and above 

 this a pair of further projecting spinous plates overhang the arm facets and mark 

 the widest part of the calyx. First iBr large, followed by two plates, and then 

 two ranges more connecting with others in the tegmen, each bearing a short, 

 central spine; anal area similar, with three plates in the second range, and 

 leading to a subcentral opening in the tegmen. Arm openings two to the ray; 

 facets very small; arms unknown. Tegmen moderately lobed, perfectly flat; 

 all plates bear one or more small spines, the largest being on the posterior oral 

 and the tegmenal axillaries at the margin above the arm bases; oral plates large 

 and well defined. Column facet large and round. 



Type. In the author's collection. 



Horizon and Locality. Hamilton Group of the Middle Devonian. Charles- 

 ton, Clark county, Indiana. 



The description is rather more of the individual specimen than is desirable, 

 but the unique type is remarkably distinct, and others would probably not show 

 much substantial variation in the characters stated. The spiny ridges and 

 rows passing from basals up the radial series give to the calyx a strikingly angular 

 appearance, unlike that of any other of the genus. From the extremely small 

 size of the facets I suspect there was something peculiar about the arms; but we 

 may not expect to see them, as they are almost never found preserved in the 



