The marine Carboniferous of North-east Greenl. and its Brachiopod Fauna. 587 



In the limestone boulder, N.o loi there are 3 fairly complete 

 specimens of the ventral valve — 2 of them younger ones (figured 

 here) and 1 older one. There are, in addition, 2 fragments of ven- 

 tral valves. Of the dorsal valve, there is one imperfect specimen. In 

 the limestone boulder, N.o 197, from the Eskimo Naze (together 

 with Pr. pseiidohorridus Wiman) there are 3 partly fragmentary spe- 

 cimens of the ventral valve, 2 younger and 1 older; in the limestone 

 boulder, N.o 196, also from the Eskimo Naze, a younger, fairly 

 complete specimen of a ventral valve. From Henrik Kröyer's Islets 

 there was obtained (N.o 191), an older specimen, partially silicified. 



The available illustrations of younger specimens (Stuckenberg, 

 1875, PI. 1, Figs. 5, 6, 7, and Tschernyschew, 1902, PI. 57, Figs. 

 3 a, 3 b) do not spread sufficient light on the structure of the spe- 

 cimens in question, but both Stuckenberg in his original diagnosis 

 and Tschernyschew state that the sinus of the ventral valve begins 

 at the apex itself and gradually increases outwards towards the 

 anterior margin and that ears are wanting in the young individual. 

 Our figures, 11 — 13, shows plainly that no ears can be distinguished 

 and that the hinge-line is straight and very short; here, too, we 

 have one of the characteristics distinguishing the younger specimens 

 from the older, viz., that the hinge-line becomes longer with age, 

 just as the valve, in general, increases in width. In one respect, 

 possibly, our specimens differ both from the Russian and those from 

 Spitzbergen, viz., that, nearest the beak, the median portion of the 

 ventral valve is rather greatly compressed, so that it abruptly 

 rises above the flanks and increases rapidly in width. The specimen 

 shown in Figs. 14 — 16, is older than the specimens which are de- 

 signated by Stuckenberg and Tschernyschew as young. The oldest 

 specimen obtained from North-east Greenland has a width of about 

 43 mm., but is not so strongly involute and, consequently, not so 

 old as TscHERNYSCHEw's oldest specimens, PI. 57, Figs. 4, 5, 6, even 

 if this specimen is not very much superior in width, its maximum 

 in this respect being only 50 mm. The specimens from Spitzbergen 

 are much wider (75 — 80 mm.) and yet at the same time they do 

 not present by far such a degree of involution as that shown by 

 TscHERNYSCHEw's figures. For the sake of comparison, the reader 

 is referred to Wiman's Fig. 20, PI. 17. In the above respects, Pr. 

 timanicus probably presents a fairly considerable space of variation, 

 so that the mentioned difference in the appearance of the species, as 

 found in the several localities, might possibly be made the basis for 

 distinguishing various types. 



The dorsal valve found here has been of fairly considerable 

 dimensions, the width being about 35 mm., without spines, and does 



