208 



PALAEONTOLOGY OF NKW-VORK. 



fingers throughout. In like manner the arms of each pair are separated at their base by an 

 elongated subconical plate, having usually two short sloping sides below, resting upon the 

 upper sloping sides of the two arm-plates of each pair (sometimes, or perhaps in each individual, 

 one or two of these plates are truncated at base, and rest upon a short truncated upper edg« 

 of the scapular plate, separating entirely, the arm-plates (see fig. 2 a) ), and separating the 

 hands and fingers of the same pair ; these plates support, on their upper side, an elongated rib 

 similar to that between the pairs of arms, which likewise reaches to the summit, and, together 

 with the five other similar ribs, supporting the ten plates or tubercles at the base of the proboscis ; 

 proboscis short, depressed conical, composed near the base of ten rows of hexagonal plates ; 

 surface of the plates of the body, and sometimes of the arms and fingers, ornamented by oval 

 or elongated tubercles, of unequal size, and, in the larger plates, frequently radiating from the 

 centre. 



This beautiful and interesting species presents considerable variety of appearance, from some 

 of which perhaps distinot species may be constituted. After examining a larger number of 

 specimens, however, I have doubted the propriety of making such a separation, for all the 

 varieties, at present. The principal forms observed are represented on Plate 47 ; fig. 1 pre- 

 senting the upper part much contracted and conical, while in fig. 2 it is proportionally shorter 

 and broader : the plates in these two are but slightly ornamented. In the specimens fig. 3, the 

 upper part is much elongated, but continues very full and round nearly to the summit, where it 

 contracts more abruptly. In fig. 4 the surface is highly ornate, and the markings continuing on 

 the surface of the fingers and the intervening ribs ; while fig. 5 presents an equally ornamented 

 surface, but of less conspicuous and somewhat different character. The two last are most con- 

 spicuously different, and will follow the descriptions of the preceding figures. 



Regarding, accoriling to the description, the direct scries of plates from the base upward 

 as constituting the pelvic, costal and scapular plates, the last supporting a pair of arm-plates, 

 we have a structure differing in a very prominent feature from any crinoid of a pentapetalous 

 base known to me. This difference consists in having the basal plates supporting, in direct line, 

 the succeeding plates to the base of the arms. I have examined numerous specimens, without 

 being able to find any evidence of a series of plates lower than those termed pelvic ; and the 

 form of these being straight across the base, and curving around to the form of the column, to 

 which they distinctly adhere, seems to preclude the possibility of finding other plates below 

 these. To avoid admitting this anomaly, we are compelled to consider as costal plates those 

 termed in the description of Prof. Phillips, as intercostal ; and the plates there termed costal, 

 as intercostal plates ; regarding the scapulars as alternating with the costal plates, and resting 

 upon their sloping edges. This gives to the most conspicuous plates of the second series the place 

 of costals, while the smaller are regarded as intercostals ; and this view is in accordance with 

 the structure of the greater number of species, so far as regards the first two series of plates. 

 Should we ever be able to discover a series of plates below those given, CA'cn if not extending 

 to the outer margin, we may regard the series as described, with the exception that what are 

 now termed pelvic will be regarded as costal plates. 



