208 SMITHSONIAN INSTITUTION 



and of two primibrachs in the other rays instead of three; and still more markedly in the 

 construction of the anal area, which is filled in the lower part by solid plates suturally united 

 with the adjacent rays. This last character differentiates it from Taxocrinus upon grounds 

 of family rank. 



It was in this species that I first 1 observed the peculiarity in the right posterior ray which 

 has been found to cut an important figure in the classification and phylogenetic history of the 

 whole group, viz., an arrangement suggesting the presence of an extra primibrach, i. e., a 

 radial followed by three primary plates in the series, instead of two as in all the other rays. 

 This appearance is caused by the fact that the two lower plates in this ray are the represen- 

 tatives of a compound radial transversely divided, the lower half being a radianal, located in 

 its primitive position as an infer-radial, resting upon the basals, and directly under the super- 

 radial as in the Inadunate genus Dendrocrinus. It is in the direct median line of the ray, in 

 contact with the radial next toward the right, and having the shape and almost the size of the 

 radials in other rays. This fact was not indicated by the principal published figures of 

 Cyathocrinus tuberculatus, upon which we had previously relied for an understanding of its 

 characters. Neither Miller's original figure (Nat. Hist. Crin., 1821, p. 88) which was copied 

 by Schlotheim, nor Goldfuss's Figure A (Petref. Germ., 1826, taf. 58) which was copied by 

 Pictet, show anything of it ; nor does Phillips's figure of another specimen in Murchison's 

 Silurian System, plate 18, nor Roemer's of still another in Bronn's Lethaea Geognostica, 

 taf. 4, figure 16. None of these but Goldfuss's shows the posterior side. Quenstedt (Handb. 

 Petref., 1885, taf. 75) copied both Goldfuss's and Roemer's figures, but in addition gave an 

 original figure (11) of the posterior side of another specimen from Dudley, in which the extra 

 plate in the right posterior ray is plainly seen. It appears in the figure to be on the left side, 

 but this is due to the reversal of the drawing in printing. Out ef 19 specimens in my own 

 collection showing the posterior side, and 15 in the British Museum, only one has two primi- 

 brachs in each ray, while all the others have the primitive radianal. Upon the evidence it can- 

 not be doubted that this is a fixed and constant structure, and on this ground I proposed in 

 1902 to separate the species tuberculatus from Taxocrinus under the present generic name 

 T emtio crinus. 



Several of the published figures show the presence of a good-sized interbrachial plate, 

 but it has not been known until now that these plates, either directly or after another range of 

 smaller plates intervening, are succeeded by a plated integument of small irregular pieces 

 passing from them, and sometimes from intersecundibrachs also, into the perisome of the 

 tegmen. This structure appears very plainly in several of my specimens, and is perfectly 

 shown in the beautifully preserved example illustrated by figure 5 on Plate XVI. The anal 

 side is similarly constructed, but has a greater number of larger solid plates filling" the lower 

 part of the area, and shows a tendency to develop a series adhering to the right posterior ray. 



This genus is one of the few occurring at Dudley which has not been found either in 

 Gotland or America. It is represented exclusively by the type species, the only modification 

 being due to variations in the marginal nodes of the brachial plates in a few specimens, and in 

 the degree of the tubercular ornamentation, none of which are sufficiently constant to mark a 

 different species. 



1 American Geologist, vol. 30, 10x12, p. 94. 



