Maryland Geological Survey: Cambrian and Ordovician

Front Cover
Johns Hopkins Press, 1919 - Geology
0 Reviews
 

What people are saying - Write a review

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

Common terms and phrases

Popular passages

Page 189 - These bodies are made up of irregular, concentric laminae of greater or less density and of very unequal thickness. The substance between the concentric lines, in well-preserved specimens, is traversed by numerous, minute, irregular canaliculi which branch and anastomose without regularity. The central portions of the masses are usually filled with crystalline, granular, and oolitic material and many specimens show the intrusion of these extraneous and inorganic substances between the concentric...
Page 37 - TYSON, PHILIP T. Second Report of Philip T. Tyson, State Agricultural Chemist, to the House of Delegates of Maryland, Jan.
Page 280 - Shell transversely elliptical oblong, height about half the length of the shell, with the beak approximately a third of the length of the shell from the anterior end. Umbonal ridge low, distinctly defined along its cardinal border where it makes an angle of 162 to 165 degrees with the longitudinal axis of the shell. Above this umbonal ridge, the posterior cardinal slope of the shell is flattened and subalate. The posterior part of the hinge-line extends from the beak for a distance equalling about...
Page 274 - ... sinuous at the middle. Dorsal valve with a rather shallow, undefined mesial sinus of moderate breadth at the front, but becoming rapidly narrower, and less impressed posteriorly, so as often to die out before reaching the umbo ; surface on each side of the sinus gently convex centrally, and sloping gradually to the lateral margins ; beak but slightly prominent and incurved. Ventral valve, with a low mesial ridge, corresponding to the sinus of the other valve, excepting that it is generally most...
Page 274 - ... slightly prominent and incurved. Ventral valve, with a low mesial ridge, corresponding to the sinus of the other valve, excepting that it is generally most prominent near the middle, and somewhat depressed anteriorly; while on each side of the ridge the slopes are distinctly compressed; beak small, abruptly pointed, projecting beyond that of the other valve, and rather distinctly arched; but not so closely incurved as to conceal the small fissure, which seems to be closed below by a deltidium,...
Page 241 - ... the costae, and often obscure or obsolete .upon their exposed surfaces; valves nearly equally convex, without sensible depression or elevation on either one, meeting at the edges in a straight line ; cardinal line not extending beyond the width of the shell; area narrow, dorsal foramen extending to the beak."— Hall, 1847.
Page 35 - Observations on the Geology of the United States of America, with some remarks on the effect produced on the nature and fertility of soils by the decomposition of the different classes of rocks. With two plates. 12mo. Phila., 1817. 1818. MACLURE, WM. Observations on the Geology...
Page 42 - CLARK, WILLIAM BULLOCK. The Relations of Maryland Topography, Climate and Geology to Highway Construction. Md. Geol. Surv., vol.
Page 281 - Shell of medium size, subovate, a little the highest posteriorly, compressed convex, thickest slightly above and in advance of the middle. Anterior margin regularly but rather narrowly rounded; base forming a broad semi-elliptic curve; posterior margin broadly rounded, very slightly oblique; dorsal outline more or less strongly arcuate, passing gradually into the ends. Beaks small, compressed, projecting very little beyond the hinge margin, placed between one-fourth and one-fifth of the length of...
Page 258 - Rafinesquina alternaia, crossed by exceedingly delicate concentric lines and over the central flat disc of each valve by more or less continuous zigzag undulations or wrinkles. " Ventral valve depressed-convex over the greater portion of the shell and more or less suddenly bent downward or geuiculated along the margin, especially anteriorly.

Bibliographic information