Mr. E. Billings on the Structure of the Crinoidea cCr. 251 



Scymnus compunctus from the former, and tlic Tenebrt'o Paivcc 

 from tlic latter. And when wc likewise include an additional 

 Philhijilrus for 8. Antonio, 8. Vicente, 8. lago, and Brava, 

 the exact numbers (as hitherto ascertained) for the respective 

 island-c^iixXoinxcs, will stand as follows : — 



S.Antonio 115 S. lago 129 



8. Vicente 134 Fogo 95 



8. Nicolao 27 Brava 62 



XXVI. — Notes on the Structure of the Crinoidea, Cystidea, 

 and Blastoidea. By p], BiLLiNGS, F.G.8., Palaeontologist 

 of the Geological Survey of Canada*. 



1. Position of the Mouth in relation to the Anihulacral System. 



The earlier paleontologists, Gyllenhal, Wahlenbcrg, Pander, 

 Hisinger, and others, described the large lateral aperture in the 

 Cystidea as the mouth, apparently on account of its resem- 

 blance to the five-jawed oral ap])aratu3 of the sea-urchins. In 

 his famous monograph, ' Ueber Cystideen,' 1845, Leopold von 

 Buch advocated the view that it was not the mouth, but an 

 ovarian aperture, and that the smaller orifice usually situated 

 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 ' Palaeontology of Newj York,' and by most others who 

 have described these fossils, including myself, in my first paper 

 on the Cystidea of Canada, published in the ' Canadian Journal' 

 in 1854. In 1858 I re-investigated the subject while preparing 

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

 apertm'e 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 ambula- 



" From Silliraan's American Journal of Science, July 18G9. 



" This paper waa prepared for the press last December; but as my 

 collection of the Blastoidea was small, I thought it best to delay publica- 

 tion until I could examine a greater number of specimens. In January I 

 applied to S. S. Lyon,I]sq., of Jetfersonville, Indiana, and he replied that, 

 if I would let him know what points I wished to investigate, he would 

 supply me with the materials. On my giving him the desired informa- 

 tion, lie, in the most liberal manner, sent me a large collection (much 

 larger than I expected to receive ), consisting of numerous specimens of 

 several genera, many of them in the state of preservation best adapted 

 for investigation — some of them empty and others silicified in a matrix 

 of limestone. Prof. E. J. Chapman (Professor of Geology and Mineralogy', 

 Univ. Coll. Toronto ) also kindly supplied me with several Russian Cysti- 

 deaus. To both of these gentlemen I here tender my thanks." — E. B. 



17* 



