NIAGARA GEOUP. 



225 



Fig. 1 u. The interior of a specimen, preserving thin sharp ridges, marking the direction of the 

 grooves to the margin of the plates. The specimen preserves a part of three costal 

 and three pelvic plates, with the larger part of two scapular plates. The costal plate 

 is a hexagonal one, and its lateral joining edges are marked hy fascicles of grooves 

 n, n, which proceed from pores in this and the adjoining plates on either side. The 

 basal edges of this costal plate, and the two adjoining ones, unite with the basal 

 plates along the line marking the greatest width of the fascicles of grooves o, o, 

 which are almost continuous ; and the same is likewise true of the junction of the 

 scapular plates with the costals, as marked in the line p, p. 



This fragment shows, in a very satisfactory manner, the arrangement of the 

 grooves proceeding from the pores ; proving the intimate connexion between the 

 organs protruding from these pores, if not their continuation from one plate to the 

 other in the interior. 



The arrangement of the pores and the little grooves proceeding from them, upon 

 the inner side of the plate of Hemicosmites, has been shown by M. Volborth 

 (Trans. Imp. Min. Soc. St. Petersburgh, 1S45 - 6). The analogy between this genus 

 and Caryocrinus, even in these minute details, is very remarkable ; and yet the 

 former is destitute of arms, has a lateral ovarian aperture, and a central proboscis. 

 These characters show more clearly how near is the Caryocrinus to Cystideans, and 

 suggests whether it should not be included in this family. 



Fig. 1 V. This figure represents the structure of this species from the base to the summit of the 

 scapular plates, showing one or two of the succeeding plates, and the relative position 

 of the arms and the mouth. The latter organ, it will be perceived, is not directly 

 over the centre of the hexagonal plate, but a little on one side, and, if the plates 

 were brought together, would rest over the centre of the scapular plate on the right 

 side of the vertical line*. 



Fig. 1 z. A view of the summit of a specimen, where the plates are well preserved, but the 

 form has suffered a little distortion. See similar figure on PL 49 a, where the form 

 of the summit is distinctly triangular. 



Fig. 1 y. The structure of the summit or crown of another specimen, showing the arrangement 

 of the plates, arms and mouth, in reference to each other, and to the scapular plates. 



Fig. 1 z. An enlargement of a portion of the column of fig. 1 d, showing the crcnulated edges of 

 the joints. 



PLATE XLIX A. 



Fig. I a. An individual of this species, preserving a portion of the column more than seven 

 inches in length. The body is compressed, and has been a long time macerated, so 

 that the tubercles and apertures of the pores are not prominent. This specimen is 

 interesting, not only as showing the long portion of the column connected with the 



* The mouth has been described as composed of six plates or valves, and this number is all that usually appear. In 

 very perfect specimens, however, there will be found an inner series, of three or four plates, protruding beyond the 

 others, and alternating with them. One of the six outer ones is usually less conspicuous than the other five, giving 

 the appearance of a pentapetalous proboscis. In one example there are three plates in the inner series, and one of 

 the six outer ones is elongated to equal and oppose them. 



[ Paljeontology — Vol. II.] 29 



