LETTER XXIV. 



BR1AR.EAN PENTACRINITE VERTEBRAL COLUMN VERTEBRAL 



PROCESSES. ...TWOFOLD OFFICE BONES FORMING THE PELVIS 



SUPERIOR EXTREMITIES ANASTOMOSING PENTACRINITE. 



THE species of pentacrinite which first demands our attention is the 

 one which most abounds in this country. This circumstance, and 

 that of its being the species which has been longest known to orycto- 

 logists, give it a fair claim to this preference. The distinguishing cha- 

 racteristic of this species appears to be its vertebral processes passing 

 out from every part of its column. 



In the trunk of this animal, are several circumstances of a 

 very interesting nature. The constant intermixture, in various ways, 

 but chiefly in an alternate order of thicker and thinner vertebrae is 

 observable, I believe, in most of the specimens of this fossil : but so 

 nicely are these vertebrae arranged and fitted ; that, except where they 

 have been displaced by accident, they always seem to preserve an 

 exact linear regularity. It is not, indeed, common to see any well 

 connected column of this species detached from its matrix, but 

 in no one specimen, however long it may have been, have I ever seen 

 the least diminution or tapering of the column. This last-mentioned 

 circumstance is particularly deserving of attention, since from it may 



