CRIXOIDS AND BLASTOIDS. 175 



DOHYCRI.VUS IMMATURUS (nOV. 8p.) W. & Sp. 



PI. XYII. Fig. 17. Posterior sides of a specimen with arms. 

 PI. XVII. Fig. 6. Another specimen, showing anterior side. 

 Pi. XVI, Fig. 5. The calyx, showing the position of the anal opening. 



The specimens are below medium size, measuring from an inch 

 to an inch and a half to the tips of the arms. Dorsal sidi of 

 the calyx subturbinate with slightly convex sides; the lates 

 convex and without ornamentation. The vault is conical, some- 

 what flattened posteriorly. Color of the specimens rather dark. 



Basals short, truncated, extending laterally beyond the limits 

 of the column; suture lines distinctly defined. First radials 

 comparatively large, almost as wide as high ; the lower margins 

 convex, the upper concave; upper corners truncated. Second 

 and third radials very short, not more than half the width of 

 the first, but twice as wide as high; the second quadrangular; 

 the third pentangular. Secondary radials 2x2x5; resembling in 

 form the two upper primary radials, but somewhat smaller. 

 The upper plates are axillary in the four lateral rays, where they 

 support 2x2 tertiary radials with two arms each ; in the anterior 

 ray quadrangular, with only one arm to each side, thus giving 

 18 arms to the species. 



Arms biserial. arranged in groups around the calyx, and sepa- 

 rated interradially by small plates. There are no inter-axillary 

 plates although the main divisions of the rays are readily 

 identified. The two arms which constitute these divisions are 

 in four of the rays arranged in pairs, being connected laterally 

 by the proximal arm plates. 



Interradials three in the dorsal cup, two of them at the 

 brachial zone, and others above. First iiiterradial very large, 

 extending beyond the limits of the third primary radials; twelve- 

 sided, and nearly as wide as high. The two plates above are 

 elongated, small, but larger than those succeeding them in the 

 vault. First anal much the largest plate in the calyx; sup- 

 porting three plates in the second range, which are nearly as 

 larg*- 1 as the first regular iiiterradials: the middle one, or second 

 anal plate, smaller than the other two. These again are suc- 

 ceeded by several smaller plates forming a protruding subcentral 

 anus which is lateral, but placed above the arm bases. 



