56 PLATYCRINID^ — CARIOCRINUS. 



farthest from the mouth. Whether the rays bifurcated or were single none of the 

 specimens hith.'rto developed offer any illustration whatever. 



Figure 3, e, table 7, represents a portion of a crinoid's ray, composed of five bands of 

 joints, wliich was obtained from the Lockport shale, along with the bodies and columns 

 of Cariocrini. It may, tlierefore, probably belong to that animal. Its structure is very 

 similar to the rays ol Sofjciiocriinis, the only known crinoid which departs so widely from 

 the usual structure and arrangement observed in the rays of the Crinoiilea, (Pinastella,) 

 and where the rays are composed of more than two series of joints, and instead of being 

 sulcated or channelled, have each a central canal for the passage of the muscles, and 

 fleshy substance of the animal. 



Mr. Say describes the Cariocrinus ornalun as possessing only six ra}s, but Mr. Lvell's 

 specimens from which our figures are taken, clearly shew ten points of attachment for 

 arms. 



The Column is circular, and perforated by a small round tubular canal. It is composed 

 of sets of three thin and smaller joints, alternating between every two tliicker and larger 

 ones. This arrangement may be modified according to the position tiie several parts 

 occupy in relation to the boily and base, but most ol' the purtions of columns we hme 

 met with liave the ossicula piled one on tlie oilier as we have described, in some 

 specimens the larger joints are studded at intervals around the circumference with 

 tubercles, similar to those frequeiUl}' seen in other columns, but \\liiLli are probably 

 merely the effects of weathering. 



The Auxiliary Side Arms. — At intervals along the column occur circular side 

 arms, the joints of which articulate by elevated radii. 



The base of attachment appears to be formed by branches around the column. 



Mr. Say describes a second species of Cariocrinus, the loricalus, which Dr. Bigsby 

 found in the same localitj^ as the C. ornnttis, but as only one specimen has been developed, 

 and the specific definition is not very satisfactory, it may probably be only an occasional 

 variety of the orjfa^/s We ha\e come to this conclusion from the circumstance that of 

 the various specimens we have examined, only one species is to be found, and also from 

 the fact that Mr. Say has described the perisomic plates (costals and scapulars) of the 

 ornntus erroneously. Therefore, when he saj's of the loricalus, "Costals five pentagonal, 

 and one hexagonal. Resembles the preceding, but there is only one hexagonal costal 

 plate, and one intei scapular plate ;" we are led to believe that the plates of the specimens 

 described from M'ere not so well defined as to ensure correctness in the description. Or 



