198 PALiEONTOLOGY OF NEW-YORK. 



without definite arrangement, or in concentric lines parallel to the 

 margins of the plate, and often elongated in the same direction, some- 

 times even forming continuous ridges. The pectinated spaces on the 

 basal plate, and on 12 and 13, are elongate reniform, and those on the 

 adjoining plates are triangular; neither being symmetrical or equi- 

 lateral. From twenty to thirty bars may be counted in each of the 

 pectinated spaces. 

 Column composed of two distinct parts : the upper, consisting of about 

 fifteen articulations, is flexible ; and the lower part, larger and of 

 greater length, consists often of nearly twice as many joints, which 

 are anchylosed together, and usually covered on the exterior by a 

 calcareous secretion of greater or less thickness. 



This fossil is better known in the rocks from the occurrence of numerous spiudle- 

 ibrm bases of the columns, which taper gradually downwards, and contract abruj^tly 

 at the upper end : these being solid, are preserved entire, while the upper parts of 

 the column, with the body, have been destroyed. These columns are often silicified, 

 sometimes entirely free from any marks of articulations, but, when well preserved, 

 presenting a granulose surface; the granules often arranged along the line of the 

 joints, but sometimes indiscriminately scattered over the surface. When these solid 

 bodies are partially worn, the articulated character is distinctly shown; and they 

 are seen to be composed of plates with deeply striated articulating surfaces, which 

 are thus strongly interlocked. In the upper part of the column the outer margins 

 of the joints overlap the next one below, and the jointed structure may sometimes 

 be traced into the upper part of the solid portion. The lower part of the column is 

 rarely preserved without thickening of the surface, as in fig. 7. 



The form of the body is like ./ipiocystites of the Niagara group, but more expanded 

 in the upper part, and with a greater proportional dissimilarity between the auteal 

 and posteal half of the body. It differs much from Callocystites, and indeed from 

 all the other cystidians of the Lower Helderberg and Niagara group, none of which 

 are known to possess the character of having Jhe lower half of the column solid. 

 In the arrangement of the arms there is no essential diiference between this and 

 Callocystites or Jipiocystites, except that in this one the ossicula are somewhat more 

 prominent above the plates of the body. 



Tlie species has a wide distribution, having been found in fragments over many 

 hundred miles in extent, and indeed almost wherever the formation is known; and 

 the great numbers of these fragments indicate the abundance of the species in these 

 ancient seas. 



