NIAGARA GROTJP. 



193 



Genus DENDROCRINUS {nov. gen.). 

 [Gr. 5EV(5pov, arbor, and xpivov, liliurn,.^ 



Calyx obconical, large ; pelvic plates five, minute ; second and third series of plates large ; 

 scapular or arm-bearing plates five, resting upon the upper oblique edges of the third series of 

 plates ; the truncated second costal plate supports the interscapular plates, the upper of which 

 sustain a series of plates forming an elongated proboscis ; arms and fingers composed of 

 single series of joints without tentacula. 



The specimen figured presents peculiarities quite sufficient for the establishment of a new 

 genus. It is the only crinoid yet observed in this geological period possessing an elongated 

 proboscis, and having the arms originating below the summit of the cup. 



587. 1. DENDROCRINUS LONGIDACTYLUS («. sp.). 



PL. XLIII. Fig. I a - fc; and Pl. XLII. Fig. 1 a, b. 



Cup large, obconical ; pelvic plates scarcely visible ; second series of plates nearly straight 

 across the base ; third series of plates having one or more truncated on the upper side, and 

 supporting an interscapular plate, which again supports a second interscapular plate ; the latter, 

 together with the oblique upper edges of the upper scapular plates, support four plates which 

 form the base of the long proboscis; arms slender, composed of a single series of joints resting 

 on the depressed upper edge of the large second scapular plate, bifurcating on every fifth, 

 sixth or seventh plate ; proboscis composed of several series of hexagonal plates, placed one 

 above another in a direct line, and alternating with a similar series on either side ; plates of 

 the proboscis strengthened by a strong vertical ridge connecting them throughout, and smaller 

 ridges diverging from the centre to each side, meeting similar ones from the ailjoining plate. 



The structure of this very singular crinoid was not fully understood from an investigation of 

 the specimen figured on Plate 43, fig. 1 a. The long slender fingers only were at first visible, 

 and it was after much labor that their connexion with the body was ascertained. In working away 

 the stone still farther, the interscapular plates were found to be connected with another series, 

 as shown in that figure, and finally the base of a proboscis was clearly traced. The full extent 

 of this portion was not suspected until the fortunate discovery of another specimen by Col. 

 Jewett, figured on Plate 42, where a large part of the proboscis is preserved, while the arms 

 are broken off near the base. 



The same side, apparently, is presented to view in both specimens. The second costal plate, 

 directly in front, is truncated above, while those on each side are angular. The structure, so far 

 as ascertained, is shown in the upper part of fig. 1 6, pl. 43 ; while the form of the two 

 second costals not seen, is conjectural. The plates are obtusely angular, as if bent, the ridges 

 running towards the angles. The surface of the calyx is marked by no peculiar ornament, 

 but appears to be simply granular. It is difficult to distinguish the true form and arrangement 

 [Paleontology — Vol. ii.] 25 



