Dr. J. Allan Thomson — Brachiopod Morphology. 73 



T. subrotunda, and T. semiglobosa. Now of these three species, 

 according to Davidson's figures, T. subrotunda is non-plicate, T. carnea 

 has incipient dorsal uniplication, while T. semiglobosa is incipiently 

 hiplicate. In Liothyrina, therefore, if we accept Buckman's view of 

 the genus, the species form a series from non-plicate to dorsally 

 biplicate. 



Terebratula itself is a dorsally biplicate shell, the forerunners of 

 which, in Buckman's * view, would be non-plicate, perhaps uniplicate, 

 before becoming biplicate. We may go further and state that every 

 Tertiary species with the Terebratula type of loop is either non- 

 plicate, dorsally uniplicate, or dorsally biplicate. No ventrally 

 uniplicate forms are known in the Tertiary of either hemisphere, 

 although there is a Jurassic genus, Glossotkyris, Douville, which has 

 this type of folding. Where, then, are we to place the recent abyssal 

 species 'Terebratula tvyvilli, Davidson, subsequently assigned by 

 Davidson to Liothyris, a shell showing pronounced ventral 

 uniplication ? Its type of folding excludes it at once from Liothyrina 

 and Terebratula, and it can hardly be supposed that Glossotkyris could 

 retain its characters with such persistence through so many millions 

 of years. It seems necessary to create a new genus for its reception, 

 but I refrain from this step in the hope that some one who has access 

 to specimens will compare its internal characters with those of 

 Glossotkyris and obtain evidence of another kind that will make the 

 way clearer. It may further be suggested that the sub-family 

 Terebratulinse, in which Schuchert includes indiscriminately shells 

 showing series from non-plicate to dorsally biplicate, to ventrally 

 biplicate, and to extreme folding of the Cincta type, is unwieldy and 

 in need of revision. 2 



Sub-family Magellanin^;. 



Turning next to the Magellaninae, we find a much greater 

 uniformity in type of folding. Douville considered that Magellania 

 flavescens, the genotype of Magellania, belonged to the ' Coarctatce' ', 

 that is, that it possessed ventral biplication, while M. lenticular is 

 belonged to the Cinctat, and he therefore made the latter species the 

 type of a new genus, Neothyris. In the case of M. flavescens, 

 Buckman, apparently overlooking Douville's statement, declared that 

 it showed a little indication of ventral uniplication. I think, 

 however, that Douville was justified, for in many specimens the 

 anterior commissure shows a dominant ventral uniplication on which 

 is imposed the beginnings of biplication. In any case it cannot be 

 doubted that many Australian Tertiary species assigned to Magellania, 

 e.g. M. gambierensis (Etheridge fil.), 3 possess distinct ventral 

 biplication. 



In the case of M. lenticularis, however, Douville was mistaken, for 

 it is not in the Cincta stage, but, as its anterior commissure shows, 

 is just passing out of the lenticular stage to incipient ventral 



1 "Brachiopod Nomenclature : the Genotype of Terebratula" : Ann. Mag. 

 Nat. Hist., ser. VII, vol. ix, pp. 525-31, 1907. 



2 See further remarks on this point under the Dallinin.E. 



3 Ann. Mag. Nat. Hist., ser. IV, vol. xvii, p. 19, pi. ii, figs. 4a-d, 1876. 



