90 



4. — Notes on the Structure of the Crinoidea, Ci/stidea and Blastoidea.^ 

 The following Notes were published in the American Journal of Sci- 

 ence and Arts, (2) vol. 48, July, 1869 ; vol. 49, Jan., 1870, and vol. 50, 

 Sept., 1870 : — in the Annals of Natural History, vol. 5, 1870, and vol. 

 7, 1871. 



At the time when these notes were published, the single aperture in the 

 summit of the palaeozoic Crinoids was generally understood to be the 

 mouth. But since then an important change has taken place in the view& 

 of most palaeontologists who have studied the subject. The prevailing 

 opinion at present is, that the aperture in question is the anus, and that 

 what 1 call the ambulacral orifices, are the oral apertures. If this new 

 view be correct, then, of course, my reasoning in the following note must 

 fail altogether. But as I still maintain that the aperture is the mouth, I 

 shall make no alteration, but reproduce these notes as originally published^ 

 I shall make some corrections and additions at the conclusion. 



1. Position of the mouth in relation to the amhulacral sy stem. 

 The earlier Paleontologists, Gyllenhal, Wahlenberg, Pander, Hisinger 

 and others, described the large lateral aperture in the Cystidea as the 

 mouth, apparently on account of its resemblance to the five-jawed oral 

 apparatus of the sea-urchins. In his famous Monograph " Uber Cysti- 

 deen," 1845, Leopold von Buch advocated the view, that it was not the 

 mouth but an ovarian aperture ; and that the smaller orifice usually situ- 

 ated in the apex, from which the ambulacral grooves radiate, was the true 

 oral orifice. These opinions were adopted by Prof. E. Forbes in his 

 Memoir on the British Cystidea, by Prof. J. Hall in the Paleontology of 

 New York, and by most others who have described these fossils, including 

 myself, in my first paper on the Cystidea of Canada, pubUshed in the 

 Canadian Journal in 1854. In 1858 I re-invcstigated the subject while 

 preparing my Decade No. 3, and came to the conclusions that the lateral 

 aperture was the mouth, in those species which were provided with a 

 separate anus ; and that in all others it was both mouth and anus. The 

 small apical orifice I described as an ambulacral aperture. Accordmg to 

 these views, the mouth of a Cystidean does not stand in the centre of the 

 radial system, as it does in all the existing Echinodermata. On this 

 point Prof. Wyville Thompson has the following observations : 



" I can see no probability whatever in the opinion lately advocated by 



* In order to assist me in preparing these notes, S. S. Lyon, Esq., of JeffersonviUe, 

 Indiana, and Mr. Wachsmuth, of Burlington, Iowa, kindly lent me large collections of 

 their beautiful Crinoids. Prof. E. J. Chapman, of Univ. Coll., Toronto, also supplied me 

 with several Russian Cystideans. To all these gentlemen I here tender my thanks. 



