The marine Carboniferous of Xortli-east Greenl. and its Brachiopod P'auna. 573 



Width 34 mm., length 23 mm. : width : length = 100 : 68 



— 30 — — 15 — — : — = 100:50 



— 26 - — 11 — — : ~ = 100:41 

 -16— — 6— — : — = 100:37.5. 



Fig. 1 shows these shell-contours. 



The differences from specimen I, described above, occurring in 

 specimens II and III, are briefly, as follows. Sp. II possesses a 

 broader and deeper sinus which is sharply limited from the lateral 

 portions of the valve; sp. Ill has the sinus relatively broad and 

 shallow, and passes fairly evenly into the lateral parts of the valve. 

 As far as regards the ribs of the sinus, sp. II appears to correspond 

 perfectly with sp. I, while, in the case of sp. Ill, the sinus in the 

 posterior part of the valve seems to have 3 ribs and, in the anterior 

 part, 5; both specimens show fairly clearly that, of the wings occur- 

 ring in the juvenile stages, there have been formed well developed 

 ears. 



The specimen I described above is in very close agreement with 

 TscHERNYSCHEw's Figs. 3 and 4, PI. XLI, which figure younger indi- 

 viduals, but the North-east Greenland specimen attains only ^ r. the 

 size of the specimens from the Urals. The older specimens figured 

 by TscHERNYSCHEW — PI. XLI, Fig. 1, for example, differ consider- 

 ably from our sp. I, and still more from our older specimens, II 

 and III. The above-mentioned figure possesses, with a width of 80 

 mm., a length of 35 mm., which gives a proportion of 100 : 44. In 

 the shell-sculpture, too, it presents considerable differences, as it has 

 much coarser ribs, which, in general, are doubled. Tschernvschew 

 compares these older specimens with Sp. grandicostatus M'Cov. 



A comparison with Tschernyschew's figures shows that the 

 only difference between our form and his figures of specimens from 

 the Urals are, in addition to the dimensions, the general contour 

 which, during growth, alters in a specially distinctive manner. In 

 the juvenile stages, the form of the shell agrees fairly well — judg- 

 ing by the striæ of growth on Tschernyschew's figures, at least — 

 and, in the form from the Urals, the superiority of width over length 

 is retained during the entire period of growth, in about the same 

 proportions. 



Of allied species, special mention may be made of Sp. trigonalis 

 Martin, but a comparison with de Koninck's figures at once show\s 

 the fairly great difference, both in sculpture and form. Another 

 species, to which one would be more inclined to refer these Green- 

 land specimens, might be Sp. Strangwaysi Vern., but, from Traut- 

 schold's figures (PI. XXXV, Fig. 4) which, it is true, are not very 

 successful, the differences are of sufficient importance to allow us 

 XLin. 43 



