410 Bibliographical Notices. 



tually accepted as correct. They have also been remarkably success- 

 ful in elucidatiug the structure, and so fixing the systematic position, 

 of that very singular form ^tejiluvnoi-rinvs, which has been variously 

 referred to the Crinoids, Cjstids, and Blastoids. The American 

 authors show, however, by the aid of some unusually perfect mate- 

 rial, that it is really a Brachiate Crinoid " with branching biserial 

 arms, given oft' in a somewhat similar manner as the aims in the 

 Platycriuida}." We are veiy glad to find thtm now admitting that 

 the ventral pyramid above the mouth is composed of orals, and not 

 of calyx-interradials *, and that Stephanocrimis is allied to AUage- 

 crinns and Haplocrinus. But we cannot at all follow the argu- 

 ment by which they endeavour to prove that this oral pyramid ia 

 homologous with the central plate which they have discovered in the 

 dome of some specimens of Haplocrinus mespiliformis. A full dis- 

 cussion of this question, however, would be impracticable at present ; 

 and the same may be said with respect to the concluding " Notes on 

 the Underbasals and Top Stem-joint of Neocrinoidea and Palaeo- 

 crinoidea." The authors claim that the symmetry of the top stera- 

 ioint in the Apiocrinidaj is interradial, and that the family is conse- 

 quently built i;pon the plan of dicyclic Crinoids. There is one slight, 

 difficulty in the way of this theory. The top stem-joint certainly 

 has interradial angles in somewhat less than half the species of 

 Ililhricrinus ; but in Guettardicrhtus, Apioerimis, and in the majority 

 of the species of Millericnnus the angles of this top stem-joint are 

 distinctly radial, and the explanation given of this awkward fact by 

 Messrs. "Wachsmuth and Springer is that the plate " attained its 

 radial angles accidentally by adapting its form to the basal con- 

 cavity, which is naturally angular '' (p. 297). 



"We are certainly somewhat surprised to be told that the structure 

 of the upper stem-joint, which presents itself in two out of the three 

 genera and in the majority of the species of the Apiocrinidse, and 

 is especially characteristic of this family as distinguishing it from 

 the Pentacrinidas is an " accidental " one f. But the authors are 

 thereby enabled to make the generalization on p. 299, " that the 

 top stem-joint is disposed interradially in the Apiocrinidte, Penta- 

 crinida?, and Comatulse, similar to dicyclic Palseocrinoids." The top 

 of the ccntro-dorsal certainly has interradial angles in the adult 

 Comatula ; but its angles are radial before the cirri appear, as is 

 permanently the case in Ajnocn'mis, and the symmetry changes 

 when the radials grow faster than the basals and come to rest 

 directly on the centro-dorsal. But we cannot understand in the 

 least how this proves that the Comaiulce " are built upon the plan 

 of dicyclic Palteocrinoids ; " and considering that in Pentacrinus 

 and also in some species of Ilillencrinns the symmetry of the axial 

 canal is interradial, a character which we cannot regard as having 

 been attained " accidentally," wo are inclined to believe that of the 



* See Ann. & Mag. Nat. Hist. March 1886, p. 282. 



t If the basal concavity " naturally ' has radial angles, is it not a 

 " natural " and not an " accidental " circumstance that the top stem-joint 

 which occupies this cavity should also have radial angles ? 



