OLD AGE IN BRACHIOPODA — A PRELIMINARY 

 STUDY 



H. W. SHIMER 



The following paper was prepared as the result of studies pur- 

 sued at Harvard University under the direction of Professor R. T. 

 Jackson, to whose oversight and suggestive criticisms the writer 

 is indebted. Thanks are also due ^Ir. R. H. Willcomb of Ipswich, 

 Mass., for his kindness in taking the photographs. 



In this study we have made use of the fine collection of the 

 Student Paleontological Department of Harvard University, the 

 collections of the Boston Society of Natural History, and those 

 of the Massachusetts Institute of Technology. Unless otherwise 

 stated, the specimens referred to are in the Student Paleontological 

 Laboratory at Harvard University. Those from the jNIassa- 

 chusetts Institute of Technology are either still in that institution 

 or have since been transferred to the Boston Society of Natural 

 History. 



This paper aims to summarize the principal characters which 

 accompany old age in brachiopods, to illustrate them with some 

 typical examples, and to present a few suggestions as to their 

 origin and meaning. 



Following the present usage, we employ the terms, nepionic 

 for the larval or postembryonic stage of an animal's individual 

 development; neanic for the immature or adolescent; ephebic 

 for the mature or adult; and gerontic for the senile or old. Each 

 one of these is further subdivided into three substages by the j^re- 

 fixes, ana-, meta-, and para-, denoting the beginning of a given 

 stage, its culmination, and its decline (Hyatt, '94, pp. 390-397; 

 '93, pp. 93-108). 



Si xirj-; ('irARACTERs 



Senility is ex[)rcssed in the shell by one or more, frequently all, 

 of the following characters: — 



