• 



x 



the Morphology of the Blastoidea. 231 



deed, of the Echinoderms generally, that we are justified in 

 demanding the most conclusive evidence of it. 



Komer's original specimens of E. Verneuili having the 

 peristome closed by the summit-plates, he was led to regard 

 tha lateral opening as an oro-anus ; and although this mis- 

 conception was set right by Hall and others, it was still 

 advocated by Billings*, with whose peculiar views respecting 

 Crinoid morphology it harmonized most admirably. We 

 think, however, that it may now be regarded as entirely 

 extinct. 



These summit-plates are often arranged with a singular 

 regularity, which is much more apparent than is usually the 

 case in other Blastoids. liomer figured seven, one in the 

 centre and six peripheral. These were also mentioned by 

 Lyon, together with fifteen others, the nature of which is by 

 no means clear from his description of them. According to 

 Hall the summit is occupied by five or more plates, while one 

 of our own specimens shows a central one immediately sur- 

 rounded by seven others, with smaller ones outside them. 

 These summit-plates appear to be larger and less numerous 

 in Eleacrinus than they are in Granatocrinus, SchizobIastus $ 

 and Orophocrinus ; but we are not inclined on that account 

 to attribute to them any special morphological value, as some 



writers have done. 



We are able to confirm Billings's account of the two hydro- 

 spires on each side of the ambulacra of E. Verneuili, and 

 have also been able to make out the watervascular ring, with 

 radial trunks proceeding from it, just as in the more common 



Blastoids. 



The species of Eleacrinus appear to be as follows ; 



Pentrernites (Olivanites) Verneuili, Troost MS. Corni- 



ferous formation (Devonian), Kentucky, Ohio, &c. 

 Olivanites annularis, Lyon. Ditto. 

 Nucleocrinus elegans, Conrad. Hamilton group (Upper 



Devonian) , New York. 

 N. lucina, Hall. Ditto. 

 N. Conradi, Hail. Upper Helderberg group (Lower 



Devonian), New York. 

 ? Granatocrinus Kirhwoodensis, Shumard. St.-Louis 



tA 1 



Limestone (Subcarboniferous), Missouri. 



(Upper Devonian), Ontario, Canada. 



Hamilton group 



• Loc. cit. , . 



t It is very doubtful whether this species is really distinct from JEL 

 iucina. Montgomery strongly suspects it to be so, but does not give a 

 definite opinion. 



