neio Species of Crinoids. 171 



can be clearly distinguished beneath the smaller cirri. This 

 extension of the cirrus-sockets over more than a single stem- 

 joint occurs also in other Palreocrinoids, and is well shown in 

 Poteriocrinus rostratus, Austin* ; it is also the case in some 

 of the recent Pentacrinidge, as, for example, in Metacrinus 

 nobilis, H. Carp.f , in which both the joint above and that below 

 the nodal joint share in the formation of the cirrus-socket. 



The nodal portion of the stem is somewhat expanded, but 

 the increased thickness is rather owing to the cirri than to 

 an enlargement of the stem itself. The sockets of the cirri 

 are slightly sunk below the surface of the stem. Only the 

 lowest four or five joints of the cirri are preserved in any of 

 the specimens ; they have a slightly oblique direction in rela- 

 tion to the stem, but I cannot say whether upwards or down- 

 wards. The faces of the joints are circular ; they vary in 

 diameter from 1 to 1*5 millim. in the smaller cirri, and about 

 2'5 millim. in the larger, and the joints are about '4 millim. 

 in thickness. The cirrus-joints are united to each other by 

 radiating unequal ridges and grooves, which are proportionally 

 larger and less numerous than those uniting the joints of the 

 stem (PI. VI. fig. 16). There are from twelve to fourteen 

 ridges, which extend nearly to the centre of the face, most of 

 which bifurcate about halfway to the margin leaving a deep 

 groove between, and there are also short ridges between the 

 larger. There is a minute central canal in the cirri about 

 •15 millim. in width, which is bordered by a slightly elevated 

 collar. 



The cirri in the same whorl are not horizontally equidis- 

 tant from each other, and, at first sight, their disposition 

 appears to be altogether irregular ; but closer consideration 

 shows, in many instances, an appearance of a bilateral ar- 

 rangement. Thus frequently there are two cirri in a whorl 

 in close proximity, whilst a considerable space separates the 

 remaining three from this pair and from each other. Now, if 

 a line is drawn between this pair through the stem, it bisects 

 the base of the cirrus on the opposite side ; and this cirrus, 

 which I regard as the anterior one (PL VI. fig. 14), has the 

 remaining two of the five at about equal distances on either 

 side of it. As this disposition can be traced in several in- 

 stances, it can hardly be of an accidental character. In each 

 of the horizontal interspaces between the cirri of the larger 

 whorls, with the exception of that between the paired cirri, 

 there are usually two laterally compressed blunted spines, one 



* Monogr. Reo. and Foss. Crinoids, pi. ix. fig. 2 a, 

 t L. c. p. 14, pi. xli. fig. 5. 



