308 STUDIES IN EVOLUTION 



Terebratalia, and Ballina. The lower genera, therefore, do 

 not progress to the final stages. 



Macandrevia King. Laqueus Dall. 



Dallina Beecher. Milhlfeldtia Bayle. 



Eudesia King. Kingena Davidson. 



Terebratalia Beecher. Ismenia King. 



Trigonosemus Koenig. Platidia Costa. 



Lyra Cumberland. 



Magellaniin^, n. sub-fam. 

 Loop composed of descending and ascending branches, pass- 

 ing in the higher genera through metamorphoses comparable 

 to the adult structure of Bouchardia, Magas, Magasella, Tere- 

 bratella, and Magellania. The lower genera become adult 

 before reaching the terminal stages. 



Magellania Bayle. Megerlina Deslongchamps. 



Terebratella d'Orbigny. Bouchardia Davidson. 



Magasella Dall. Kraussina Davidson. 



Magas Sowerby. 



MEGATHYEINiE Dall. 



Loop composed of descending branches only, passing in the 

 highest genus through stages correlative with Qivynia, Ois- 

 tella, and Megathyris. The lower genera do not complete 

 the series. 



Megathyris d'Orbigny. Zellania Moore. 

 Cistella Gray. G-wynia King. 



References. 



1. Agassiz, L., 1873. — Methods of Study in Natural History, eighth 



edition. 



2. Crane, Agnes, 1893. — The Distribution and Generic Evolution of 



some Recent Brachiopoda. Natural Science, vol. ii. 



3. Dall, W. H., 1870. — A Revision of the TerebratulidiE and Lingu- 



lidse with remarks on and descriptions of some recent forms. 

 Amer. Jour. Conchology, vol. vi, pt. ii. 



