584 Karl A. Grönwall. 



if they can be fairly well supplemented by the description belonging 

 to them. 



TscHERNYscHEw's figuies give a considerably clearer picture of 

 the species, and our specimens agree very well with them, especially 

 the ventral valve — our PI. XXIX, Figs. 1 — 2 — with Tschernyschew's 

 PI. 30, Fig. 8. The only difference from the American form that 

 TscHERNYSCHEW cmphasizes, is, that, on the lower part of the valve, 

 the tubercles serving as the bases of the spines are somewhat elon- 

 gated, a feature which is clearest evident on the mould, although 

 TscHERNYSCHEW also remarks about this, that a longitudinal exten- 

 sion in the case of these tubercles can also be observed in one of 

 Derry's figures (PI. 6, Fig. 5). In our specimens, these tubercles 

 are not fully round but somewhat greater in length than width, 

 although they have not that swollen, oval form of Productus spinu- 

 losus Sow. (Davidson, 1857—62, PI. 34), to which species Pr. Walla- 

 cianus Derby has been referred by Schellwien (1900, p. 49), while 

 TscHERNYSCHEW denies the identity. 



Our specimens present a little difference from Derby's descrip- 

 tion, the hinge-line being somewhat shorter than the greatest width 

 of the shell. The case is the same in several of Tschernyschew's 

 figures, and Derby's Fig. 5, PI. 6 also shows an indication of the 

 same feature. Another difference is that, in our specimens the hinge- 

 line is faintly curved; this is especially noticeable on the dorsal 

 valve. Derby's figure 46, Pi. 3, indicates that the hinge-line there 

 is straight, while in Tschernyschew, especially in PI. 60, Figs. 22 — 

 23 indicate a curving of the hinge-line which, however, is lesser 

 than in our specimens. 



As regards dimensions, the specimens from North-east Greenland 

 agree with those given, both from Russia and from Brazil. 



The species occurs in the Cora- and in the Schwagerina hori- 

 zons in the Urals. 



As to the identity of our species with the Pr. cfr. Wallacei from 

 the mosquensis strata of Spitzbergen described by Holtedahl (1911, 

 p. 31, PI. 5, Fig. 14), it is impossible to form any decided opinion 

 based on Holtedahl's description and figures. 



N:o 23. Productus Lovéni Wiman. 



PI. XXVIII, Fig. 23. 



Wiman p. 72, PI. 17, Figs. 12—18. 



Of this species there is in a boulder of grey limestone {N:o 204) 

 collected at Eskimo Naze, a fairly well preserved specimen, which, 

 on splitting the rock, showed itself in such a way that both the 

 dorsal and the ventral valve appeared as a cast, the visceral room 



