The marine Carboniferous of North-east Greenl. and its Brachiopod Fanna. 559 



The two specimens at our disposal must, as regards dimensions, 

 almost be considered as small ones, their width, length and thick- 

 ness being, respectively, 18, 17.5, 12 mm., and 15.5, 15, 10 mm. Both 

 present some indication of a sinus, the larger specimen to a greater 

 degree than the smaller. Both in their proportions and in form 

 they agree very nearly with smaller specimens figured by Waagen, 

 e. g., on his PI. 40, Fig. 10 a— d, only that the latter are somewhat 

 broader. Waagen mentions specimens 46 mm. broad, while Da- 

 vidson, for A. Royssii, gives a width of 70 — 80 mm., and for A. 

 pectinifera, about 30 mm. 



If a distinction of species is to be maintained, our specimens 

 must be referred to A. Royssii L'Eveillé, but the slight material at 

 our service gives no guidance in solving the chief question. From 

 another quarter, however, it should be possible to obtain an argu- 

 ment to show that a complete ontogenetic series of these species 

 would probably present transitional forms and variations so closely 

 connected with each other that these two species, A. Royssii and A. 

 pectinifera, must be classified as but one. We allude here to the 

 development series of the closely related species, A. Royssiana Key- 

 serling, that WiMAN, 1914, p. 30, PI. 1 and 2, has figured from the 

 Spirifer limestone of Spitzbergen. Regarding this series, which con- 

 sists of more than 40 specimens, Wiman states as follows : "Irgend 

 eine Correlation der Merkmale lässt sich nicht beobachten und die 

 Variation ist richtungslos. Überhaupt zeigt diese Serie wie unvor- 

 sichtig es ist, Artbeschreibungen auf zu kleines Material zu gründen. 

 Aus der abgebildeten Serie könnte man leicht Exemplare aussuchen, 

 die man als zu verschiedenen Arten gehörig betrachten könnte, wenn 

 man nicht die ganze Serie hätte, und doch ist in diesem Fall die 

 Erhaltung tadellos". 



According to Davidson, A. Royssii is a species occurring abund- 

 antly in the Mountain Limestone of England and Belgium, while A. 

 pectinifera occurs spread through the Permian of England, Germany 

 and Russia. According to Waagen, A. Royssii is also found in the 

 Permian deposits of Russia, and, according to Tschernyschew, A. 

 pectinifera occurs already in the Cora horizon, and continues into 

 the Permian. In the East Indies, according to Waagen, A. Royssii 

 is found in the upper and middle parts of the Productus limestone 

 in the Salt Range, and the same writer has described several nearly 

 related forms as independent species. Diener, in several works, has 

 described both A. Royssii and nearly related species, both from the 

 Productus limestone, and from higher, Permian deposits. No strati- 

 graphical importance, therefore, can be ascribed to this form. 



42* 



