6. DEVELOPMENT OF TEREBRATALIA 

 OBSOLETA Dall* 



(Plates XXIV and XXV) 



Fischer and CEhlertf have given a full account of the 

 development of the brachial supports in Terebratella dorsata 

 and Magellania venosa, from Tierra del Fuego. This work, 

 together with that of Friele,J and Deslongchamps,§ on the 

 northern species Maoandrevia cranium and DalUna septigera, 

 and the equatorial species Muhlfeldtia sanguinea, constitute 

 nearly all that is known regarding the metamorphoses taking 

 place in the brachial supports during the growth of an indi- 

 vidual belonging to the higher genera of the Terebratellidse. 



It is of interest to add another species to this list, espe- 

 cially as it represents a northern form, the development of 

 which has not been hitherto studied. This form offers, more- 

 over, some additional features for comparison, and two very 

 early stages have been discovered which are both of genetic 

 value. 



The material for this work has been kindly furnished by 

 Dr. William H. Dall, of Washington. The specimens were 

 dredged by the U. S. steamer Albatross, in 113 fathoms, at 

 Station 2984, off Cerros Island, Lower California. In a 

 report on some shells from this expedition, by Dr. Dall, || 

 this brachiopod was described as Terebratella occidentalis, 

 var. obsoleta. Subsequent study, however, has led him to 



* Trans. Conn. Acad. Set., IX, 392-395, 398, 399, pis. ii, iii, 1893. 



t Bull. Soc. Hist. Nat. d'Autun, V, 5 plates, 1892. 



t Arch. Math. Nat., Bd. XXIII, 1 877. 



§ ifetudes critiques des Brachiopodes nouveaux on peu connus, 1884. 



II Proc. U. S. Nat. Mas., XIV, 1891. 



