22 T7-ans. Acad. Sci. of St. Louis. 



the reader, I will recapitulate the various views of our most 

 distinguished palaeontologists concerning this question, which 

 will show that very little attention was given to anatomical 

 differences, and that all specimens enumerated in this genus 

 were placed there on merely external resemblances. If anat- 

 omical differences had been considered, Shumard would never 

 have proposed to put species like Granatocrinus norwoodi, 

 curtus, gramdatiis, sayi, roemeri, cornutus, etc., into one 

 genus* 



In 1861, Meek and Worthen say, in speaking about Pen- 

 tremites cornutus and Pentremites meIo:'\ " Both of these 

 forms differ from the typical species of the genus Pentremites 

 in having each pair of ovarian openings distinctly separated, 

 instead of closely united with merely a thin septum between. 

 In this character, as well as in form, and the prolongation of 

 the pseudo-ambulacral areas, they agree with the genus 

 ISfucleocrinus of Conrad {=^ Elaeacrinus, Roemer), from 

 which they differ in having the anal and oral openings dis- 

 tinct as in the true Pentremites. Thev constitute a sub- 

 genus of Pe7itre?nites, occupying a position between the 

 typical forms of that genus and yucleocrinus.^' 



In 1862 Prof. Hall says in speaking about the genus jSTu- 

 cleocrinus: J — 



" Regarding only the general form of these bodies, this 

 genus would include several species, heretofore described 

 under Pentremites, from the Carboniferous limestones of the 

 Western States, viz. : Pentre^nites norwoodi, Owen and 

 Shumard; Pentremites nielo, Owen and Shumard; Pentremites 

 curtus, Shumard, and others ; while the Pentremites ( Olivan- 

 ites) verneuili = Elaeacrinus verneuili, Eoemer, and Olivan- 

 ites angidaris, Lyon, are of the age of the upper Helder- 

 berg limestones; and the JSfucleocrinus elegans, Conrad, and at 

 least one other species, occur in the Hamilton group. The 



* Roemer's Pentremites granulatus is taken as type of the gerius. — See 

 B. F. Shumard, Transactions of The Academy of Science of St. Louis, Vol. 

 IL,p. 375. 



t Proceedings of The Academy of Natural Sciences of Philadelphia, 1861, 

 p. U2. 



X Fifteenth Annual Report of the Regents of the University of the State 

 of New York, p. 145. 



