1886.] NATURAL SCIENCES OP PHILADELPHIA. 223 



Zittel suggested (Handb. d. Palseont., i, p. 390), that the plate 

 which connects with the basals in Apiocrinus probably repre- 

 sented an anchylosed underbasal disk, composed of five pieces. 

 That this is impossible is shown by the case of Mill, polydactylus, 

 which in that case would have two rings of underbasals. We 

 fully agree with De Loriol and Carpenter that it is an enlarged 

 stem joint, and believe that the plate represents morphologically 

 the top joint (the first one beneath the basals) of all Crinoids, 

 recent or fossil. The plate forms no integral part of the calyx, 

 but rests in all cases either against the dorsal (outer) face of the 

 basals, against the underbasals, or against both of them. It is 

 disposed interradially in the Apiocrinidse, Pentacrinidse and Com- 

 atulfie, similar to dicyclic Pal^ocrinoids, and undivided ; while in 

 other groups it is sometimes compound (tripartite or quinquepar- 

 tite). The underbasals, however, form an integral part of the 

 calyx, they rest within the basal ring, against the lateral faces of 

 the plates, and they are composed primarily of five pieces, which 

 occasionall}' are reduced by anchylosis to three, or coalesced into 

 a solid disk. If this is correct, it follows that the inner plate of 

 Stemmatocrinns, Cupressocrinus and allied genera is not a stem 

 joint, as suggested by Carpenter (Chall. Rep. 153) and others, 

 but an anchjdosed underbasal disk, as seen by examining the 

 inner side of the calyx, which shows that the plate forms a part 

 of the calyx, and rests against the lateral faces of the basals, 

 within the basal ring, and not against their outer faces. 



ADDITIONS AND CORRECTIONS. 



Owing to peculiar circumstances preventing a suificiently careful super- 

 vision of ljublication (although the proofs were carefully examined by one 

 of the authors), a number of errors have been detected, especially in the first 

 section of Pt, III. Two or three of these are exceedingly annoying, entirely 

 changing our meaning. We request our readers to make the changes at 

 once in their copies as indicated below. 



Part I. 



On p. 239 (Ex. Ed., p. Ki), 6th line from bottom, for "Palseocrinoids" 

 read ^'Pcntacrinoids.''^ 



On p. 251 (Ex. Ed., p. 28), 16th line from top, for "first radials" read 

 "basals''^ (although the interpretation thus indicated has been modified 

 by us). 



On p. 324 (Ex. Ed., p. 101), 11th and 10th line from bottom, change 

 twice: "radial" into '^interradial,^^ and " interradial " into "radial'^ 



