36 Redeics — Wachsmuth 8^ Springer's Monograph on Crinoids. 



Dendrocrinus (Figs. 12 and 13). Thus EA altered in outline, and 

 was brought into contact with other anal plates ; first with x (as 

 in Dendrocrinus and Homocrlnns, Fig. 7), then also with rt (as in 

 Poteriocrinns and allies, Fig. 14), while it might even support 

 a third plate to the right of rt, as in some species of Parisocrinns 

 (Fig. 16). In some later genera, such as Zeacrinus (Fig. 8), 

 EA increased in size and rt was again raised above the level of the 

 cup; while in Ulocrinus (Fig. 3) the plate x also was (to use 

 Wachsmuth and Springer's expression) " crowded out by the large 

 radianal." In other genera, however, EA became reduced and 

 finally disappeared (e.g. DeJocrimis, Fig. 9). 



To turn to rt, the plate which in Poteriocrinns (Fig. 14), Atelesto- 

 crinus, and similar forms rests between x and r.post.E and on EA, 

 and therefore in the limits of the cup : it is admitted that this 

 is subsequently pushed up out of the cup (e.g. Zeacrinus and 

 Ulocrinus, Figs. 8 and 3) ; further, that it was at an earlier stage 

 resting on the left shoulder of r. post. Es (e.g. Dendrocrinus and 

 Homocrinus, Figs. 12, 13, and 7). To this extent I am in full 

 accord with Messrs. Wachsmuth and Springer, and would point out 

 that this admission stultifies their distinction between anals and 

 tube-plates, and allows that a tube-plate can sink down into the cup. 



In Heterocrinus (Figs. 5 and 17) and Ectenocrinns a single plate 

 at the base of the tube rests on the shoulders of the two posterior 

 radials, which are here not separated by any anal plate. This 

 proximal single plate is considered by Wachsmuth and Springer to 

 " take practically the place of the three plates \lt, rt, and mt'] in 

 Dendrocrinus." They also homologize it with the proximal tube- 

 plate of Hyhocrinus, which they say on pp. 129, 130, 133 has 

 a similar position. This is a peculiar slip, for their own figure 

 shows that this plate in Hyhocrinus lies between the posterior radials 

 on a large radianal (Fig. 6). They also homologize with this the 

 proximal tube-plate of locrinus (p. 130) and apparentl}' Merocrinus 

 (p. 128); but this plate rests only on the right posterior snperradial, 

 absolutely outside the cup, and is removed by the whole height of 

 that plate from the left posterior radial (Figs. 4 and 11). If, therefore, 

 these homologies of Wachsmuth and Springer be accepted, it follows 

 that the plate in question {t in their figures, x in ours) moved either 

 from a position well above the radial circlet (locrinus) to one-half 

 within it {Ectenocrinns), and finally entirely within it {Hyhocrinus), 

 or in the reverse direction. Either view is in direct contradiction 

 to their statement on p. 132 that "there was no sinking of the 

 plate t, which never moved from its place above the radials." That 

 is another of those dogmatic general assertions which are useful 

 to dispose of other people's theories, but are overlooked when the 

 opinions of Messrs. Wachsmuth and Springer would be invalidated 

 by them. 



Eightly or wrongly (in the main, I believe, rightly) our authors 

 have thus far explained the modifications of the anal area 

 in Inadunata on principle 4 of the above list, namely, by the 

 shifting, atrophy, and growth of certain constant elements. But 



