193 



tirely disappointed. In this whole mass, in which is a connected se- 

 ries of vertebrae of nine inches in length, and which may fairly be 

 extended to more than three times that length, by reckoning the dis- 

 placed pieces which it is evident were once in continuation with it : 

 in this mass, in which not half an inch is free from the vertebrae of 

 this animal, and in which it may be safely inferred, that some of the 

 vertebral columns passed through the whole length of the slab, not 

 the least trace of any regular termination can be discovered. Its ex- 

 amination, however, furnished the following facts : 



In this assemblage of vertebrae, which there is every reason to sup- 

 pose must have belonged to one particular species of this animal only, 

 a very considerable variety of form and of combination may be dis- 

 covered : some being exactly the same size, forming a column uni- 

 formly smooth and even ; some being alternately larger and smaller, 

 forming a column with alternate risings and depressions ; some be- 

 coming gradually larger, and then again contracting in size, and there- 

 by acquiring a bulging form ; and others having regular articular de- 

 pressions in their sides for the reception of lateral processes. Besides 

 these, a great number of varieties are here observable, too many, in- 

 deed, to allow of being particularized ; and sufficient to shew, that it 

 would be rather difficult to detect the species of the animal by the 

 form and appearance of the vertebrae. 



The general character of the trochitae of this species appears, how- 

 ever, to be, that they are pierced with a much larger foramen than 

 that which is observable in trochitae of other species. The trochitae, 

 Plate XIII. Fig. 29, and Fig. 42, appear to have belonged to this spe- 

 cies ; as well as the silicious cast, Plate XV. Fig. 10, and the casts 

 existing in the mass of screw-stones formed of chert, and represented 

 Plate XV. Fig. 6. 



In another slab from the same place I was, however, more success- 

 ful, it containing that part of the skeleton of the body which has 

 been called, in the stone lily, the pentagonal base. It, however, dif- 

 fers essentially from the corresponding part in that species, as appears 



VOL. n. cc 



