252 Mr. F. M'Coy on some new Palceozoic Echinodermata. 



or more rows of interambulacral plates, instead of two as in those 

 of the newer rocks and existing seas ; as therefore those sea-nrchins 

 differ from all of the order Echinida in the great number of rows 

 of plates in the test, usually having an odd number of rows in the 

 interambulacra, and the consequent impossibility of theoretically 

 dividing them at the sutures into five equal parts, I would pro- 

 pose to form a peculiar order for their reception under the above 

 title, indicating the complexity of their structure. I first drew 

 attention to the structural peculiarities of those fossils in 1844 

 in my ' Synopsis of the Carb. Limest. Fossils of Ireland ' (p. 171 

 to 174), where I gave the generic charactei's of the genus Prt/<e- 

 chinus (proposed in manuscript by my friend Dr. Scouler), and 

 described and figured several species having from three to five 

 rows of plates in the interambulacra. In the same work I stated 

 that the plates of the so-called Cidarites of the carboniferous 

 period being hexagonal was a proof that they too must have had, 

 like the Palcechini, more than two rows of interambulacral plates, 

 and being consequently distinct from the newer fossil and recent 

 Cidaris, I mentioned that I had long distinguished them in 

 manuscripts (in the collections at Dublin) under the name of 

 Ai-chceocidaris. In that work I withdrew my own name however 

 in favour of Echinocrinus, by which M. Agassiz had announced 

 his intention of designating the carboniferous Cidaris Nerii, &c. 

 in his Introduction to the 2nd livr. of his ' Monog. des Echinod. 

 Fossiles,' p. 15 : although he did not either define the genus 

 or recognise the aforesaid peculiarities, the name itself seemed 

 to indicate an entirely different affinity, namely with the Cri- 

 noidea, in which group this generic name is placed in Agassiz's 

 ' Nomenclator Zoologicus.' I propose to resume now my old 

 name for this genus, 1st, because M. Agassiz neither indicated 

 the affinities nor gave any descriptive notice of the genus Echi- 

 nocrinus, while I have done both for my Archcsocidaris ; 2nd, se- 

 veral of the continental geologists have not followed my example 

 in rejecting my own name, but prefer Archceocidaris ; 3rd, in the 

 ' Catalogue Kaisonne des Echinodermes,' &c., published by MM. 

 Agassiz and Desor in the ' Annales des Sc. Nat.^ for November 

 1846, no mention is made of the genus Echinocrinus, but the 

 species which were to have formed the ty])e of it {Cidaris Nerii, 

 &c.) are given under the new title of Pakeocidaris, which of 

 course has no claims for adoption on the score of priority; nor 

 do MM. Agassiz and Desor even there seem aware of the pecu- 

 liarity in form of the interambulacral plates or their abnormal 

 number, although my observations on those points are mentioned 

 by M. Verneuil nearly two years before in his ' Coup d'oeil general 

 sur la Faune Paleozoique de Russie,^ prefixed to the second vol. 

 of MM. Murchison, Verneuil, and Keyserling^s great work on 



