280 Dr. P. H. Carpenter on the 



described by Rbmer *, who expressly stated that the sutures 

 "between the pore-plates and the lancet plate only become 

 visible when the surface of the arabulaeral field has under- 

 gone a certain amount of weathering. This explains the 

 absence of the suture in the " entirely well preserved speci- 

 mens " mentioned by Mr. Hambach. His dictum that the 

 sutures would be visible if the markings in question were 

 only surface-ornamentation, will not accord with the expe- 

 rience of those palaeontologists who are continually obliged to 

 rub away the surface-ornamentation on the bodies of Crinoids 

 and Urchins in order to see the sutures between the plates. 

 Mr. Hambach attempts to prove the correctness of his asser- 

 tion respecting the preservation of an elastic integument 

 covering the ambulacra by the following argument f, which 

 I quote in full, in the hope that others may be able to under- 

 stand it better than I can : — " Or, how would Mr. Carpenter 

 explain the presence of those large and strange bodies in the 

 interior of the calyx, which are frequently found in entirely 

 pet-feet and undisturbed bodies, if the acute points of the 

 integument were not flexible? Such and similar specimens, 

 I should think, would afford sufficient proof of the correctness 

 of my assertion." 



It will be remembered that in Mr. Hambach 's first paperj 

 he made the somewhat comprehensive statement that the 

 central summit-opening of the Pentremites " was never closed 

 by additional plates, as intimated by some authors." The 

 existence of a group of minute plates in this position had 

 been described and in some cases figured by Owen and Shu- 

 mard§, Billings||, C. A. White If, Meek and Worthen**, and 



* ' Monographic der fossilen Crinoiden-Familie der Blastoideen, und 

 der Gattung Pentatrematites im besondern ' (Berlin, 1852), pp. 13, 14. 



t Trans. St. Louis Acad. vol. iv. p. 540. 



t Ibid. p. 150. 



§ " Descriptions of one new Genus and twenty-two new Species of 

 Crinoidea from the Subcarboniferous Limestone of Iowa," Keport Geol. 

 Survey of Wisconsin, Iowa, and Minnesota, 1652, p. 5L;2. See also B. F. 

 Sbumard, " Descriptions of new Species of Blastoidea from the Palaeozoic 

 Bocks of the Western States, with some Observations on the Structure 

 of the Summit of the Genus Pentremites,'' Trans. St. Louis Acad. Sci. 

 vol. i. 1858, p. 243, pi. ix. tig. 4 ; and likewise Palseontological Report 

 to Swallow's First and Secoud Ann. Reports Geol. Survey, Missouri, 

 1855, p. 180, pi. B. tig. 1 c. 



|| " Notes on the Structure of the Crinoidea, Cystidea, and Blastoidea," 

 Ann. & Mag. Nat. Hist. ser. 4, vol. v. 1870, p. 265. 



^f " Observations on the Summit Structure of Pentremites, the Struc- 

 ture and Arrangement of certain Parts of Crinoids, and Descriptions of 

 new Species from the Carboniferous Rocks at Burlington, Iowa," Boston 

 Joum. Nat. Hist. vol. vii. 1862, pp. 481-488. 



** ' Palaeontology of Illinois,' vol. v. \67?>, p. 4G6, pi. ix. figs. 2 a, 5. 



