NIAGARA GROUP. 



199 



Genus LECANOCRINUS {nov. gen.). 

 [Gr. Xexavi), pelvis, and xpivov, lilium ; from the bowlshaped form of the calyx in the tj'pical species.] 



Pelvis composed of three plates ; second series consisting of five, with an intercalated plate ; 

 third series, or scapular plates broad, with an interscapular plate in the same range ; arms with 

 two joints, above which are several subdivisions closely arranged, the plates uniting laterally 

 without interlocking. 



There are several species possessing characters sufficiently similar to admit of their union 

 under a single genus ; regarding minutely only the more important parts of the structure, and 

 recognizing a general similarity in habit and character of other portions of the animal. 



590. 1. LECANOCRINUS MACROPETALUS (n.5;j.). 



Pl. XLV. Fig. 1 a - fi. 



Body sub-globose ; pelvis composed of three small plates, succeeded by five costal plates of 

 very large dimensions, two of these are pentagonal, one regularly hexagonal, and two hepta- 

 gonal J a single sub-quadrangular intercostal plate ; scapular plates five, two of them pentagonal, 

 and three with a short sixth side ; a single interscapular plate ; arm-plates two, above which 

 the plates subdivide, a second subdivision occurring above the third or fourth plate from the 

 first division ; extremities of the fingers folded inward, leaving an open ca\-ity at the summit ; 

 column round, composed of smooth, alternately thicker and thinner joints which articulate 

 strongly upon their outer margins j canal rounded, with sometimes indications of a tripetalous 

 form. 



This species is easily recognized by its general form, and particularly by the structure of the 

 calyx, which is constant in all the specimens examined. The plates, to the subdivisions of the 

 arms, are remarkably large, and the wide scapular plates give great width to this part of the 

 body. The coliunn is comparatively slender, and composed of smooth thick joints, alternating 

 at irregular intervals with thinner ones. The edges of the joints of the column appear slightly 

 rounded, giving it a characteristic appearance. 



There is a very interesting analogy between this species and the Ichthyocrinus Icevis ; which 

 is the more remarkable, since the latter belongs to the division with five pelvic plates. The 

 Lecanocrinus seems, as it were, to be a farther development of the type first appearing in 

 the Ichthyocrinus. It has been shown, that at the base of the latter, and entirely covered by 

 the upper extremity of the column, are three minute plates, which nowhere reach the margin. 

 The five small pelvic plates do not entirely surround the margin, but allow a narrow portion 

 of one of the second series to rest upon the edge of the column. If we suppose for one moment 

 these three minute plates to be more fully developed, we have the pelvis of the Lecanocrixus. 

 Regarding still farther those portions of the triangular pelvic plates of the Ichthyochinus, inter- 

 vening between the outer margin of those plates and the three minute plates of the centre, to 



