NO. 2.] DESCRIPTION OF THE FOSSILS. 63 



ascertained whether it agrees with this species of the Suahian "Ornaten"-cIay 

 or not. Up to the present, no similar Pseudomonotis is known from the 

 Russian Jura, or from the Arctic regions i. The North American species, 

 Pseudomonotis (Eumicrotis) curta Hall sp.^ and orUmlata Whitfield 3, 

 appear to be allied to the present form in their delicate sculpturing. 



PECTEN, Klein. 



(Gamptonectes, Agassiz) 



Pecten Lindstromi Tullberg. 



PI. I. fig. 12. 



1881 (1880) Pecten Lindstromi. S. A. Tullberg, 'Ueber Versteinerungen aus 



den Aucellen-Schichten Nowaja Semljas'. Bihang till K. Svenska Vet. Akad. 



Handl. vol VI. No. 3, p. 24, pi. I, figs. 1—5. 



The present specimen is the impression of a moderately convex left valve. 

 Contour obhque oviform, sides somewhat unequal. Height scarcely one sixth 

 greater than the length of the valve. The partly broken and displaced anterior 

 wing is large: the posterior, smaller wing is very imperfect. The surface is 

 densely ornamented with fine, concentric lines, which appear very distinctly on 

 the wing, while on the valve itself they are only visible under the lens. The 

 concentric sculpturing is crossed by a system of extremely fine, close, radial lines. 

 These correspond (on the positive of the shell) with fine, rather long, very narrow 

 depressions, arranged in radial rows, and occurring in the interspaces between 

 the concentric lines. Near the lateral margins, and especially on the wing, 

 the radial lines appear more distinctly than elsewhere on the valve, where 

 they are only visible in a good hght. (In fig. 12b, the radial lines of the valve 

 have not been clearly brought out.) Towards the edge of the valve, the radial 

 lines are curved. 



The specimen of Pecten Lindstromi Tullb. was found in a loose block of 

 rusty-coloured, weathered, clay sandstone, on July 16th, 1896, north of Elm- 

 wood, 500 — 550 ft above the sea. 



1 The Pseudomonotis suhecMnata Lah. described by Lahusen (Die Fauna der Juras- 

 sischen Bildungen des Rjasanschen Gouvernements, p. 85, pi. II, figs. 6, 7), judging 

 from its coarse sculpturing, is closely allied to Pseudomonotis echinata Sow. sp. 



2 F. B, Meek and F, V. Haydn, 'Paleontology of Upper Missouri', part I. 1864, pi. III. fig. 10. 

 ' H. Newton and W. P. Jenny, 'Report on the Geology and Resources of the Black 



Hills of Dakota', U. S. G. a. G. Survey of Rocky Mts. Region, 1880, p. 356, pi. III. 

 figs. 17-19. 



