204 PROCEEDINGS OP THE PALEONTOLOGICAL SOCIETY 



SOME STRUCTURAL FEATURES OF A FOSSIL EMBRYO CRINOJD 

 BY GEOKGE H. HUDSON 



{Abstract) 



A fossil embryo crinoid is described as ;i new genus and species and named 

 Embryocrinus prohlematicus. Tlie arm structure, as shown by enlargements 

 (X 20) taken through cover-glass and gum mounting, is seen to consist of a 

 linear series of thin, irregularly formed discs or lunate pieces of stereom, in an 

 otherwise fleshy extension of epidermal or associated tissues. The structure 

 revealed is precisely like that of the spines and spinelets of Ur aster ella 

 medusa, as shown in plates accompanying the report of the New York State 

 Director of Science and State Museum for 1915. 



The methods of study and the jorogress made in the preparation of a 

 monograph on American Tertiary Bryozoa were outlined by the junior 

 author. Illustrated by specimens and lantern slides; discussed by E. M. 

 Field. 



METHODS OF STUDY AND THE CLASSIFICATION OF AMERICAN TERTIARY 



BRYOZOA 



BY F. CANU AND R. S. BASSLER 



{Al)s tract) 



The junior author showed, with the aid of specimens and lantern slides, the 

 methods of collecting, the preparation for study, and the characters employed 

 in classification of American Tertiary bryozoa now under monographic study. 

 Until recent years the post-Paleozoic bryozoa have been considered more as 

 perforated stones than as well organized creatui-es in which the perforations 

 and ornamentation of their surface had definite physiological purposes. The 

 relation between the morphological and skeletal variation and their physio- 

 logical purposes was determined in the case of the fossil forms by the close 

 study of the most nearly related living species. This study showed that (1) 

 a family is characterized by having the same larval form, or, since the larva 

 and ovicell are in rapport, by the same kind of ovicell ; (2) that the genera 

 differ from each other by possessing different functions. These functions, 

 common to all bryozoa, are as follows : 



1. Passage of eggs and escape of the larvie (= rapport of the operculum and 

 the ovicell). 



2. Hydrostatic system and extrusion of the polypide (=form of the aperture 

 and rapport of the operculum with the compensati-ix). 



3. Calcification and chitinization (=^= nature of the skeleton and of the 

 frontal considered as immediate deposits of the endocyst). 



At 1 p. m. the Society adjourned for hmclieon. 



