The marine Carboniferous of North-east Greenl. and its Brachiopod Fauna. 567 



Auernigg beds in the Carnian Alps, and PI. 47 b. Fig. 1 b, possibly 

 Sp. supramosquensis Nik. from Nova Zembla; the piece is an original 

 figured also by Toula, but as Sp. mosquensis). 



Schellwien has later on (1900, pp. 71-72, text-figs. 10 and 11) 

 more definitely pointed out the difference between Sp. Fritschi and 

 Sp. siipramosqiiensis, and has described it, while referring to Russian 

 specimens of Sp. supramosquensis. He gives as a specific characteri- 

 stic of Sp. supramosquensis the shape of the sinus of the ventral 

 valve, which possesses a markedly deeper groove in the middle of 

 the otherwise somewhat shallow depression that the sinus forms. 

 This characteristic has been observed by Wiman too in specimens 

 of Sp. supramosquensis from Beeren Eiland. This feature alone, 

 however, is not sufficient to characterize Sp. supramosquensis, as 

 Sp. Nikitini Tschern. also possesses a sinus of the same shape, 

 which ScHELLWiEN gives as distinctive for Sp. supramosquensis. 

 TscHERNYscHEW, in his description of these two species, does not 

 mention this deepening of the sinus, but gives, as the characteristic 

 features, the form of the shell, and the height and width of the 

 cardinal area. 



Sp. Fritschi is the broadest of these three species, with the width 

 of the shell considerably exceeding the length, and with the cardinal 

 area almost equal to the greatest width of the shell, fairly low, and 

 provided with a peculiar sculpture; the beak is abruptly pointed and 

 projects only inconsiderably beyond the hinge-line. Sp. supramos- 

 quensis and Sp. Nikitini are probably very nearly related, the length 

 and width of the shell are approximately equal, in both species the 

 hinge-line is shorter than the greatest width of the shell, but, in con- 

 sequence of the beak in Sp. Nikitini being higher and very sharply 

 pointed, the cardinal area in this species is both higher and narrower 

 than that of Sp. supramosquensis : in Sp. Nikitini it occupies about 

 one-half of the greatest width of the shell, while, in the case of Sp. 

 supramosquensis, it occupies about two-thirds. 



As regards the interior structure of the shell, Tschernyschew 

 points out that Sp. supramosquensis and Nikitini agree in respect to 

 the "geraden, verkürzten Zahnplatten", and that Sp. Fritschi and 

 Sp. supramosquensis can, with sufficient positiveness, be distinguished 

 from each other by means of the interior structure of the shell. He 

 does not, however, point out any special characteristic features. If, 

 however, we compare Schellwien's figure (1892, PI. V, Fig. 8) of 

 the internal structure of Sp. Fritschi with Fig. 16 and Nikitin's 

 description of the inlernal structure of the shell of Sp. supramos- 

 quensis, one can no longer feel any doubt as to the importance of 

 this difference. 



