248 



PALEONTOLOGY OF NEW-YORK. 



Fig. 21. The lower side of the specimen, of the natural size. 



Fig. 22. One of the arms enlarged. 



Fig. 23. Several of the ossicula, with the short spines as they appear bordering the avenue. 



Position and locality. In the shale at Lockport. {Collection of Col. Jewett.) 



The principal genera of CystidecB, which have been described, are given in the table on a 

 preceding page. Two other genera are added in the preceding descriptions, and one Avhich is 

 not positively ascertained, under Crinoidese. To these we have to add another form in the 

 Pentamerus galcatus limestone ; above which, we have, yet, no well ascertained species of 

 this family. It is not improbable, however, that we shall meet with species when more com- 

 plete examinations are made in the higher rocks. It is not a little interesting to observe that the 

 development of species in this family corresponds to the Crinoideee ; both being more numerous 

 in the Niagara period, than in any preceding or succeeding period of the New-York strata. 



Since the preceding pages were in type, a farther examination of a specimen of the Callo- 

 cysTiTES, which was coated with hard shaly matter, has revealed the lingers or tentacula at- 

 tached to the fragment of an arm still remaining. This has been figured on Plate 50, and 

 completes the characters of this beautiful fossil. In the same figure, is shown more distinctly 

 the longitudinal division between the bases of the arms upon the summit. 



Further examinations among specimens of Caryochinus have served to convince me that 

 the orifice termed the mouth is not the only one existing upon the summit ; and I am more 

 inclined to regard the so called mouth as an ovarian aperture, corresponding to the organ of 

 similar structure in the Cystideae. In the description of this fossil, the mouth was regarded as 

 being in the centre of the base of the triangle formed by the summit. No sufficient reason has 

 been shown why this part assumes a triangular form, which is almost always apparent in 

 well preserved specimens ; but we have an explanation of the reason why the side on which 

 the mouth is placed assumes a more direct line, from the wider space between the arms at that 

 point. Now if we regard the mouth as posterior, we shall find on the left side, near the middle 

 of one side of the triangle, an aperture or pore, which in some instances appears to be closed 

 by small plates. In no instance where it has been sought for, in this position, have we failed 

 to find some evidence of its existence. It has been impossible to pursue the examinations far 

 enough to decide the nature of this organ, or whether it be simple or two organs. 



I was led to search for an aperture in this position from the fact that the mouth and anal 

 pore in the Callocystites and Apiocystites are always on the left side of the summit, 

 regarding the ovarian aperture as posteal ; and this aperture in Caryocrinus, bears the same 

 relation to the mouth or ovarian aperture. 



On the opposite or right side of the body of Caryocrinus, there is, in several specimens, 

 some appearance of an aperture or tuberculous plate, which has not been sufficiently examined. 

 These facts induce me to believe that there is a very close affinity between this genus and some 

 of the cystidean genera. 



