282 THE CANADIAN NATURALIST. [Sept. 



whole width of the vault. G. siphonatus (Hall), figured on the 

 same plate, shows, that the anterior grooves curve round to the 

 posterior side of the proboscis, as they do in B. icosadactylus 

 above cited. 



I should also state here, that two or three years ago, Mr. 

 Meek, to whom I had written for information on this subject, 

 wrote me that, in all cases, where he had observed the grooves 

 on the interior of the vault, they radiated, not from the mouth, 

 but from a point " in front of it." (This would be not in front 

 of, but behind the mouth, according to the terminology used in 

 these notes. I think that the side in which the mouth is situa- 

 ted should be called " anterior'' or ''"oral," even although both 

 the mouth and anus should be included in it.) 



In all the species above cited, the figures (with the exception 

 of C. ornatus) exhibit the relative position of the mouth and 

 radial centre, as it has been actually seen in casts of the interior 

 of the vault. But besides these, numerous examples may be 

 found in the works of Miller, Austin, De Koninck, Phillips, 

 Meek, Worthen, Shumard, Hall, Lyon, Cassaday, and others, of 

 Crinoids whose external characters show that, in them, the mouth 

 cannot be in the central point, from which the grooves radiate. 



With respect to Prof. Thompson's theory, I freely admit that 

 if it is true that in all the echinodermata, fossil and recent, the 

 mouth is the radial centre, then, that aperture must be the one 

 which I call the ambulacral orifice in the Cystidea. The views, 

 however, advocated by me in my Decade No. 3, appear to be 

 gradually gaining ground. As these fossils are rare, few have 

 occasion to study them, and consequently the subject has not 

 been much discussed since 1858, the date of the publication of 



the Palfeozoic Crinoids, with the tubes radiating therefrom, belong to the 

 respiratory and, perhaps, in part, to the circulatory systems— not to the 

 digestive system, as is supposed by the authors. The convoluted plate, 

 with its thickened border, seems to foreshadow the " eesophageal cir- 

 cular canal," with a pendant madreporic apparatus, is in the Holothu- 

 ridea. To me the final determination of this question is of much im- 

 portance , for, if Meek and Worthen are right, then I must be wrong so 

 far as regards nearly all that I have published with reference to the 

 functions of the apertures of the Palaeozoic Echinodermata. It is for- 

 tunate that the solution of this curious problem is now undertaken by 

 men who have access to the magnificent cabinets of the geologists of 

 the Western States, and by men who habitually discuss scientific 

 subjects with the sole object in view of arriving at the truth. 



