382 C. I'J. Beecher — Revisiori of the Families of 



cardium Lam. from the Jurassic) since that genus has strong dental 

 plates in the ventral valve, dividing the cavity of the beak into 

 three chambers. Waagen'*^ shows that these features ; i. e., septal 

 and dental plates, are entitled, in the terebratuloids, to rank as 

 generic characters. 



The name Dalli:n^a, nov. gen., is therefore proposed, to include 

 shells of the type of Terebratvla septigera Loven ; as DalUna 

 Haphaelis Dall, sp., D. Grayi Davidson, sp., and D. floridana Pour- 

 tales, sp. The genus is given in honor of William H. Dall, whose 

 name has long been intimately associated with the best work on 

 recent Brachiopoda. 



There still remain the northern species heretofore referred to 

 Terehratella, which differ from true Terebratella (type T. dorsata) 

 in the same manner and degree as Dallina from Magellania. These 

 also require a special designation, and the name Tekebratalia, nov. 

 gen.., is proposed, based on Terehratula transversa G. B. Sowerby, 

 as the type. 



The earliest stages of development in the Dallina and Terehra- 

 talia branch of the Terebratellidse have been observed by the writer 

 in T. tra7isversa Sow. and T. ohsoleta Dall.* * They represent first 

 a shell without a septum in the dorsal valve, and without calcified 

 supports to the brachia, Plate I, figure A. The structure just 

 before the appearance of the septum is the same as that described 

 in Gwynia by King. The brachia form a slender fleshy ellipse or 

 circle, resting in front on the floor of the interior of the dorsal 

 valve, with the tentacles, or cirri, centripetal or directed inwards, 

 as in an early stage of Cistella. After this gwyniform stage, the 

 growth of the septum inflects the circlet of tentacles, producing a 

 condition identical with that in adult Cistella, Plate I, figure B. It 

 is therefore called the cistelliform stage. 



The succeeding transformations in Dallina septigera and 3faca7i- 

 drevia cranium have been fully described by Friele." These 

 species, with Terehratalia ohsoleta Dall, sp., make three typical 

 northern forms whose development has been observed. They agree 

 in every essential detail, and may be described in general terms. 

 The first stage described hj Friele, Plate I, figures Cl, Dl, showed 

 the growth of the descending lamellae, their union with the septum, 



* Originally described as Terebratella occidentalism var. ohsoleta^ by Dall, but now con- 

 sidered by him as a distinct species. The complete development of the brachial sup- 

 ports in this species is shown in the accompanying paper. 



