NIAGARA GROUP. l97 



Genus LYRI0CRINUS( nov. gen.). 



[ Gr. Xupiov, lyra parva, and xpivov, lilium.] 



Column round ; pelvic plates five, pentagonal ; costal plates five, restirg on the oblique 

 upper edges of the pelvic plates, and succeeded bj five scapulars, which support an arm- 

 plate, upon the oblique upper edges of which rest the hand-joints supporting a pair of 

 fingers ; a single interscapular plate between each pair of scapulars, with the two second 

 interscapular plates resting upon its oblique upper edges and the edges of the adjoining 

 costal plates. 



The arrangement of the plates in this genus commences upon the simplest plan known, 

 that of the continuation of the plates in the second series in a direct line to the base of 

 the arms. The number of plates interposed, however, between the pelvis and the sub- 

 divisions at the base of the arms, shows a higher type, which is further indicated in the 

 arms, the fingers of which are composed of a double series of plates. 



589. 1. LYRIOCRINUS DACTYLUS. 



Pl. XLIV. Fig. la- g. 

 Marsupiocrinites? da^tylus. Hall, Geo!. Rep. 4th Dist. N. York, pag. 114; fig. 4, p. 113, 1843. 



Column round, composed near the head of alternating larger and smaller joints, the 

 larger projecting much beyond the smaller ones ; canal apparently round ; surface of 

 plates finely ornamented ; pelvic plates small, pentagonal ; costal plates heptagonal, 

 scapulars hexagonal ( in one of the five there is a double scapular, and the succeeding 

 plate is somewhat smaller than in the others); arm-plates of the form of the pelvic plates ; 

 hand-juints two, one above the other, the lower somewhat cuneate, resting on each of the 

 sloping upper sides of the arm-plate ; fingers ten, composed of a double series of joints 

 interlocking with each other, gradually tapering to the extremity. The intermediate 

 plates are uniform, with one exception : a quadrangular plate is interposed between 

 the two second interscapular plates ; this point is un the opposite side from the super- 

 numerary scapular, and both may be seen in fig. 1 d. Between each pair of fingers there 

 are tv/o small plates interposed at the base, directly above the interscapulars ; and 

 between the fingers of the same pair there is a single pentagonal plate interposed, similar 

 to the larger of the two plates between the pairs of fingers. 



This species is readily distinguished by the great number of plates below the sub- 

 divisions of the arms, which take place in a direct line from the divisions between the 



