542 REVIEWS 



The exoclyclic disk and open ambulacara, and the arms, pinnules, and 

 syzygies of Actinometra ; 



The free-floating character of the Comatulae ; 



The dicyclic base of the Dicyclica ; 



The monocyclic base of the Monocyclica. 



A noteworthy feature that should receive special mention in con- 

 nection with this monograph is the distribution of study material, 

 illustrating the points and structures discussed, to some of the prin- 

 cipal museums. It is a feature that could well be imitated by other 

 workers in paleontology. In this way the principal type specimens 

 have been deposited in the Museum of Comparative Zoology. A large 

 slab has been placed in the National Museum at Washington ; it con- 

 tains specimens exhibiting most of the characters discussed. A fine 

 series of specimens have also been sent to the British Museum, and to 

 the Royal Museum of Natural History at Berlin, where they will be 

 accessible to European students. 



2. As stated by Dr. Clarke, in his prefatory note to the Oriskany 

 Fauna of Becraft Mountain, the original purpose of his work was 

 solely to depict the character and composition of the Oriskany fauna 

 of Becraft Mountain, which of itself displays many features of interest. 

 In its progress, however, various questions have arisen which concern 

 the intrinsic value of the fauna and its importance in correlation. Yet 

 without an understanding of the fauna itself it would be impracticable 

 to discuss the latter problems, and for this reason the title of the paper 

 is restricted to the principal argument of the work, to which the dis- 

 cussions of a somewhat broader scope are corollaries. 



A fauna which finds its highest development at Becraft Mountain, 

 near Hudson, in Columbia county, N. Y., links together in the char- 

 acter of its species, the calcareous shales and limestones of the Lower 

 Helderberg and the normal Oriskany sandstone. 



The interesting bearings of this assemblage of species, its new forms and 

 new associations and its real importance in the correlation of the Lower 

 Devonian are sufficient reason for presenting its characteristics in detail. 



A brief account of the stratigraphy of the mountain is given, and 

 also the general New York section as recently revised. Accompanying 

 these is a small geological sketch-map of the Becraft Mountain syncline. 



The greater portion of the memoir is devoted to the description of 

 species, which are finely illustrated by nine plates of figures. A table 

 of the vertical range of species occurring in the region is given. 



