18 PLATYCRINID^. PLATYCRINITES. 



From the spheroidal form of the body and extent of the internal cavity, it is highly 

 probable that the P. he vis, and others of the genus, possessed a liver; as also a long 

 convoluted intestine terminating in a vent. The recent HoJopus has a valvate anus ; 

 and we suppose the Platj/crinites, which are so much larger, and certainly not inferior 

 in organization, to have been furnished with a similar organ. 



Whether aeration was carried on by means of aquiferous tubes, which brought the 

 aerated water in contact with the nutritive fluid, it is cUfhcult to determine, as a careful 

 examination of several hundred specimens, has not enabled us to discover sufficiently 

 clear indications of the existence of aquiferous passages to speak mth confidence on 

 the point. We have in the Actinocrinifes discovered circular tubes communicating with 

 the internal cavity, but their office is at present unknown. 



An imperfect vascular system, with a cordal smus, we have reason to suppose existed, 

 as well as a distinct ovarial system. 



There is also decided evidence of a fibrous muscular system, which imparted mobihty 

 to the remotest extremities. 



The only slight indication of the preservation of any of the softer parts of tlie animal, 

 is that of an exceedingly hard irregularly shaped substance, which, in several instances, 

 has been observed lying across the indiuated frame work of the animal, in such a 

 manner as to give rise to the idea that the intestinal parts had oozed out of the visceral 

 cup, and become incorporated with the calcareous sediment which entombed the 

 specimen. 



The obscure associated bodies alluded to, probably contamed albumen, wliich became 

 closely incorporated with carbonate of lime, and produced a substance even harder than 

 the fossil itself. They may possibly be cojirolitic matter, though they do not resemble 

 in form the coprolites, so abundant in some beds of the carboniferous limestone. One 

 of the extraneous bodies alluded to is visibly depicted in PL 1,,^V/. 2, O. 



It is perhaps as well to remark here that the evidence on which several species of 

 crinoids have been admitted into the genus Platycrmites by various authors, is not 

 sufficiently conclusive to establish their claim to this distinction. We therefore propose 

 to omit or suppress the following species, as not appertaining to the genus, namely, P. 

 micro.sfj/lus, P. interscapularis, P. contractus, P. depressus, and P. ventricosus. 



As it is in justice due to those Authors who have endeavoured to establish species 

 which we consider altogether questionable, to explam the grounds on Avhich we have 

 rejected so many species, we wiU briefly advert to the several reasons by wliicli wo have 

 been guided when venturing to deviate from received opinions. 



The P. contractus, (Gilbertson) Pliillips, Geol. of Yorkshire, we consider as identical 

 with the P. Itevis, and we have therefore declined to contmue it as a distinct species. 



As to the P. microsti/lus, of which Mr. Phillips has not even given a figure in his 



