124 FOSSIL CRINOIDS. 



radials; large, rounded radial facets, directed outwards; a dorsal canal, or dorsal 

 extension of the axial canal, perforating the radials and arms, entirely separate 

 from the ventral or ambulacral groove; undivided infrabasals; and a quadri- 

 partite axial opening, consisting of a central canal surrounded by four smaller 

 peripheral ones, extending from the column into the base of the calyx. All of 

 these characters belong equally to Gasterocoma; the only point remaining as to 

 which a difference might be noted is the plate above the anal opening. This 

 plate may not be in any way homologous to the anal plate .t of other genera, 

 lying, as it does, anterior to the opening, and in front of whatever anal tube may 

 exist. At all events it is wholly inconstant, being present in one Kentucky 

 species, and absent in the other, as well as in the New York species; in both 

 the latter the radials meet above the opening in all specimens where the structures 

 can be distinctly seen. Hall's description of an anal plate touching the basal 

 in C. bulbosus is incorrect; the specimen in which he supposed it was (15th 

 Rept. N. Y. St. Cab., PI. I, fig. 19) is in poor preservation, the surface much 

 corroded, so that the sutures cannot all be definitely traced; it has an irregular 

 aspect, the space for the infrabasals looks four-sided, and there are possibly only 

 four basals (PI. II, fig. 3 herein). In none of the other New York specimens, 

 of which we have several much better preserved, is there any such plate as he 

 describes. 



Now as to the so-called anal plate, there is the greatest irregularity among 

 the Eifel specimens. Schultze enumerates and figures seven different conditions 

 of this, which he calls the "interradial," in as many .specimens, six of them in 

 one species, G. antiqua (Mon. Echin. Eifelk., 97, PI. XII), viz: — 



1. The typical form, with a quadrangular plate between the radials and 

 above the opening: Fig. 1. 



2. A triangular plate, with the radials closing above it : Fig. lb. 



3. Two plates, of the form and size of No. 1, bisected vertically: Fig. la 

 (erroneously marked Id, being the isolated figure between the second and thirtl 

 rows from the top; there is confusion in the designation of several of the other 

 figures of G. a/iirgwa on this Plate: 1^ should be/; l/i should be ^; 1 i should be /i ; 

 and 1/ should be k). 



4. Three plates, two smaller ones under the usual large one: Fig. Id. 



5. No plate at all, the posterior basal reaching the tegmen, and the anal 

 opening being under the right posterior radial: Fig. le. 



6. No plate, the opening directly through the posterior basal, and the 

 radials meeting above it: Fig. Ic. 



