416 Charles Emerson Beecher. 



Atrypa, JRetsia, and Terebratula" It will be noticed that 

 this arrangement of widely differing genera foreshadows 

 two orders of brachiopods for which Beecher later proposed 

 JSTeotremata and Telotremata. 



My acquaintance with Beecher began in 1889, and at that 

 time it was evident that the paper just referred to was being 

 considered with a better understanding of what Hyatt's prin- 

 ciples meant when applied to Brachiopoda. The very fact that 

 nearly all the Waldron, Indiana, brachiopods began with 

 smooth shells having a subcircular outline, led him to look for 

 this early stage in other genera, but as no other young shells 

 were at hand, he resorted to a study of the beaks in well-pre- 

 served examples of mature shells. During the fall of 1890 he 

 spent nearly a week going through my collection, and with 

 studies made on other collections he was able to announce in 

 the spring of 1891 that he had seen the initial shell in fifteen 

 families as recognized by (Ehlert in Fischer's "Manuel de 

 Conchyliologie," these being represented by forty genera. 



At this time he made the important announcement " that all 

 brachiopods, so far as studied by the writer, have a common 

 form of embryonic shell, which may be termed the protegulum." 

 The protegulum is the phylembiwonic stage of Brachiopoda. 

 A prototype preserving throughout its development the main 

 features of the protegulum was at first supposed to exist in the 

 Lower Cambrian Paterina, but as this proved to be identical 

 in structure with fphidea, the conclusion had to be abandoned. 

 However, at maturity this genus is so closely related in general 

 form with the protegulum, that we may hope at any time to 

 find the prototype. 



A study of the stages of growth in many brachiopods, from 

 the Cambrian to the living forms, enabled Beecher to show 

 that the old classifications based upon the presence or absence 

 of hinge teeth, the nature of the intestinal canal, etc., were not 

 expressive of genetic relationship. He demonstrated that on 

 the basis of types of pedicle openings all brachiopods are natu- 

 rally grouped into four orders, of which two are without and 

 two possess hinge teeth. The most primitive order [Litigula, 

 etc.) he named Atremata, and this gave rise directly to the 

 Telotremata (Rhynchonella, Terebratula, etc.). The Neotre- 

 mata {Crania, Discina, etc.) also originated in the Atremata, 



