Bulletin - United States Geological Survey, Issue 544

Front Cover

What people are saying - Write a review

We haven't found any reviews in the usual places.

Other editions - View all

Common terms and phrases

Popular passages

Page 111 - ... of the hinge; beaks moderately prominent, convex, incurved without very distinct obliquity and located about halfway between the middle and the posterior side; umbonal slopes, both before and behind, subangular, in consequence of the presence of a lunule and escutcheonlike impression, of which that on the anterior or longer side is the larger, being usually continued nearly or quite to the extremity of that side. Surface smooth, or only showing under a magnifier very obscure lines of growth.
Page 132 - XLVII, figs. 1,2,3. Shell large; length nearly equal to or slightly in excess of the width. The largest example observed must have been over 65 mm. long when complete. The hinge line is long, though somewhat shorter than the greatest width. The obliquity is slight but appears to be forward as in Lima. The convexity of the left valve is moderate or strong in different individuals. The umbo is large, well defined, and incurved. The wings are broad and the outline is not strongly withdrawn beneath them....
Page 93 - Survey, vol. 6, p. 102, pi. 12, figs. 4-4c. Upper and lower Coal Measures to base of Permian: Fort Scott, lola, Lawrence, Topeka, Kans.
Page 132 - ... which is very oblique and directed backward. Both valves seem to have this structure of the same character and force. Near the center, under the hinge plate, are several .small depressions arranged in a row, and some distance apart, which may mark the position of the pedal muscle. The shell is thick and massive, especially in the upper and older portion. It is conspicuously constructed of two layers, an outer one which is relatively thin and which carries all the more delicate surface ornamentation,...
Page 160 - The nodes vary considerably in arrangement not only in different specimens but in different parts of the same specimen.
Page 227 - ... but are obliquely truncated. This type is rather clearly not a representative of true Orthoceras, nor have I been able to find a genus with which it can be assembled. Indeed, it is not certain that it can be included among the Orthoceratidse, though to that family it is for the present referred. The most diagnostic features are probably the enlarged siphuncle and more especially the secondary deposits accumulated not axially but circumferentially.
Page 8 - ... obscurity of the contact lines, due to the friable nature of the beds, it is not possible to accurately distinguish them. The lowest of the four sandstone divisions of the Wewoka formation is thinner, though generally harder, than the succeeding ones.
Page 164 - ... Worthen, not only because they are the authentic ones, but because although B. crassus has appeared in the literature not infrequently, the citations have seldom been based on the observation of good and characteristic specimens. The most essential difference shown by the Wewoka specimens is that the umbilicus instead of being partly open, is so solidly closed that there must have been a continuous imperforate columella. The size is very much smaller ; the shape of the aperture more transverse,...
Page 111 - ... larger, being usually continued nearly or quite to the extremity of that side. Surface smooth, or only showing under a magnifier very obscure lines of growth. "Length of the largest specimen, 0.57 inch ; height, 0.40 inch ; convexity, 0.30 inch. Some of the other specimens are proportionally more convex.
Page 164 - Wewoka specimens is rather deep, but I am not sure that this feature may not have been exaggerated by erosion of the projecting band. Furthermore, on the best specimens, the callosity of the inner lip appears to be imperfectly developed. It is possible that this may prove to be the same as B. incomptus, but after comparing my specimens with Gurley's types, which I have had the privilege of examining, thanks to the courtesy of the Walker Museum of Chicago University, I am disposed to think that they...

Bibliographic information