Dr. J. Allan Thomson — Brachiopod Morphology. 75 



I believe, true Terebratella, and if this be so Terebratalia becomes 

 a synonym of Terebratella. Before this position can be disputed it is 

 necessary to study their young stages and show that they are not 

 comparable to those of Terebratella} Beecher was apparently misled 

 by the general separation of the Dallininse and the Magellaninse in 

 the northern and southern oceans. Jackson 2 has already shown that 

 the Dallininse have a species {Macandrevia diamantind) in Antarctic 

 waters, and it now appears that the Magellaninae have at least three 

 genera, Mageilania, Terebratella, and Magasella, represented in the 

 North Pacific. 



But even if it should be shown that Terebratalia is distinct from 

 Terebratella, there can be no question, on account of the difference in 

 folding, that Terebratella obsoleta cannot be referred to Terebratalia, 

 and a new genus is necessary for its reception, and this I now propose. 



Dallinella, genus nov. 

 Genotype, Terebratella obsoleta, Dall. 3 



Shell non-plicate to dorsally uniplicate. Loop passing in growth 

 through Platidiform, Ismeniform, and Muehlfeldtiform stages, attaining 

 finally a stage resembling Terebratella. The non-plicate Terebratula 

 spitzbergenensis, Dav., and the dorsally uniplicate Terebratella Maries, 

 A. Adams, may apparently also be referred to Dallinella. 



We have, therefore, in the Dallininse a recent stock of shells, 

 ranging from non-plicate to dorsally biplicate, represented by the 

 genera Dallina and Dallinella. Amongst fossil stocks with the same 

 types of folding may be mentioned Kingena, Epicyrta, Ccenothyris, 

 JPlesiothi/ris, and the multicostate genera Ismenia, Eudesia, and 

 Flabellothyris. 



But those are also genera which go through growth-stages similar 

 to those of Dallina so far as loop-development is concerned, but are 

 ventrally plicate. Macandrevia appears to be non-plicate in the 

 genotype M. cranium and not in the Cincta stage as Douville thought, 

 but M. diamantina, Dall, is clearly a ventrally uniplicate form. The 

 Recent species of Muehlfeldtia are incipiently uniplicate, and Platidia 

 also shows the beginnings of ventral uniplication. We should expect 

 to find a genus of Recent or Tertiary shells in this series with 

 Terebratelliform loop which might be regarded as the forerunner of 

 Macandrevia. Possibly this lack is supplied in the species Terebratula 

 frontalis, Middendorff, which agrees with expectations in being 

 ventrally uniplicate, in possessing an incomplete foramen and a short 

 median septum not reaching posteriorly to the umbo, but we are left 

 in ignorance by Davidson as to the nature of the hinge-teeth and 



1 The binge - plates of these species appear to be Terebratelliform, and 

 Davidson has stated that the growth stages of T, coreanica resemble those of 

 T. rubicunda. If T. grayi is correctly placed in Mageilania, the presence of 

 T ' erebratellm in the Northern Pacific is only to.be expected. 



2 J. W. Jackson, " The Brachiopoda of the Scottish National Antarctic 

 Expedition " : Trans. Boy. Soc. Edin., vol. xlviii, pp. 367-90, 1912. 



3 In case Beecher has made any mistake in his identification of this species, 

 with which I am unacquainted, I further desire to define the genotype as the 

 species actually figured by Beecher under the name of T. obsoleta, Dall. 



