414 Bibliographical Notices. 



The authors have been singularly fortunate in having access to an 

 unrivalled series of specimens, the riches of the National Collection 

 having been largely supplemented by the friendly cooperation of 

 many English and foreign palaoontologists. Most important assist- 

 ance has, in this manner, been rendered by Mr. Charles Wachsmuth 

 of Burliiagton, Iowa, who, with a generosity beyond all praise, un- 

 reservedly placed at the disposal of the authors an extremely valuable 

 series of American Blastoids, selected from his own fine collection 

 as especially adapted for the exhibition of structural characters. 

 And it is not too much to say that by means of this friendly help 

 it has been possible to interpret the details of many points of internal 

 structure which could not otherwise have been satisfactorily explained 

 at present. 



The first portion of the " Catalogue " is devoted to the morpho- 

 logy of the Blastoids generally. This section of the work is prefaced 

 by the zoological history of the group, and then follows an account 

 of the structure presented by the various forms, each plate and 

 organ being described in detail, their modifications throughout the 

 series reviewed, and their probable functions and homologies dis- 

 cussed. The geological and geographical distribution of the Blastoidea 

 is next treated of. Then follows the systematic portion of the work, 

 in which the species and higher classificatory divisions are clearly 

 defined and severally discussed. 



The much controverted question of the relative rank which should 

 be assigned to the Blastoidea among the other groups of Echinoderms 

 is reviewed in a chapter marked by great clearness of judgment and 

 logical reasoning. The authors rank the Blastoidea as a distinct 

 class of the branch Pelmatozoa, which is recognized as a primary 

 division of the Echinodermata, comprising the three eqidvalent 

 classes Crinoidea, Blastoidea, Cystidea. 



The following definition, embracing the result of the authors' long 

 and careful study of the group, will give in their own words a brief 

 conspectus of some of the important results arrived at, which for 

 want of space we are reluctantly unable to notice : — 



"Class Blastoidea. 



"Armless Pelmatozoa of a pyriform, clavate, ovate, or globose 

 shape, which usually exhibits a very perfect radial symmetry. Base 

 monocyclic, of two large plates and one small one, the latter being 

 always in the left anterior interradius (A-B). Eive radials, more 

 or less deeply incised by the ambulacra, and five interradials which 

 rest on them and bound the peristome, one of them being pierced by 

 the anus. 



" Ambulacra fringed on each side by a single or double row of 

 jointed appendages, which are in close relation with the side plates. 

 These rest on or against a subambulacral lancet-plate, which is 

 pierced by a canal that lodged the water-vessel and unites with its 

 fellows into a circumpral ring. 



" Hydrospires arranged iu ten (or rarely eight) groups, which are 



