388 PROCEEDINGS OF THE ACADEMY OF 



are tumid, and a few that extend out over the third radials become subconical. 

 The proboscis is subcentral, of medium size, and rises abruptly from the much 

 depressed vault. (Other parts unknown.) 



Height, 0*22 inch ; breadth across the disk, between the interradial spaces 

 on opposite sides, 0*33 ; do., between the third radials on opposite sides, 0"54 

 inch ; breadth of base, 0*14 inch. 



Locality and position. Burlington, Iowa. Burlington Limestone, of the 

 subcarboniferous series. 



Actinockinds ( Amphokacrintjs*) subtukbinattts. Body rather under me- 

 dium size, turbinate, or obconical below the arms, and depressed convex 

 above ; expanding regularly with straight sides from the column to the sum- 

 mit of the third radials, thence more abruptly to the arms ; composed of flat, 

 smooth or merely granulose plates, which are connected by close-fitting sutures. 

 Interradial and anal spaces rather distinctly excavated between the groups of 

 arms. Base comparatively small, subpentagonal, about one-third as wide as 

 high, and not provided with a projecting rim ; columnar facet concave, small 

 or less than half the diameter of the base. First radial plates generally a little 

 wider than long, widening from the base to the lateral angles, two of them 

 heptagonal and three hexagonal. Second radials small, about twice as wide 

 as high, quadrangular, or rarely with one of the upper angles slightly trunca- 

 ted so as to produce a fifth angle. Third radial pieces a little larger than the 

 second, about twice as wide as high, hexagonal and heptagonal, and support- 

 ing on each superior sloping side in the anterior and two posterior rays, one 

 (occasionally two on one side of the latter) small secondary radial piece, which 

 gives rise to two brachial pieces ; while in each of the two antero-lateral rays, 

 the two small secondary radials are truncated above, and each supports a single 

 brachial piece ; making two arms to each of these rays, and four to each of the 

 others, or sixteen to the entire series. 



The first interradial plates are about two-thirds as large as the first radials, 

 nearly as long as wide, and six to nine-sided. On the superior sloping sides 

 of these, rest two smaller pieces, which partly support the secondary radials, 

 and are surmounted by two or three irregular pieces, which extend up between 

 the groups of arms. The first anal piece is as large as the first radials, about 

 as long as wide, heptagonal, and surmounted by three smaller hexagonal 

 pieces in the second range, the middle one of which extends above the others. 

 Surmounting these there are also three pieces in the third range, the two late- 

 ral of which each supports an irregular piece above, while the middle one pro- 

 jects considerably beyond the others, and supports on its sloping sides a series 

 of protuberant plates, which surround the small anal aperture. 



The summit is composed of irregular unequal plates, one of which over each 

 arm, and another near the middle, are larger than the others, and appear to 

 have been convex, or may even have been extended into short spines. The 

 anal aperture is lateral, being located a little above the elevation of the arm 

 openings. 



Height from base to summit, 0*59 inch ; breadth across the summit between 

 the groups of arms, 0*60 inch ; do., from the arm openings on opposite sides, 



* We think. Austin's name Amphoracrimts should be retained, at least in a subgeneric 

 sense. The lateral position of ihe anal and oral opening in this group, instead of having 

 it placed in or near the centre of the vault, and extended in the form of a more or less 

 elongated proboscis, must have been accompanied by some marked difference in the 

 structure of the softer parts of the animal. Indeed it seems to us that in the classification 

 of the Crinoidea, too much importance is often given to the number and arrangement of 

 the pieces forming the cup, to the neglect of the ensemble of characters presented in the 

 structure of all parts of the animal. When we see whnt widely dissimilar species are some- 

 times brought together in the same groups, by the present classification, we cannot avoid 

 suspecting that it is, as now used, at least to some extent, analogous to the old artificial 

 Linnaean classification in botany, and that it will some day give way to a more rational 

 method that may make material modifications in the genera as we now understand them. 



[Sept. 



