Palaeozoic Fossils, Volumen1Dawson Bros., 1865 |
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9 lines angular Anticosti aperture apex apical angle appears axis Bathyurus beak body whorl broadly rounded Cape Norman cardinal angles Chazy cheeks CHEIRURUS Collector.-J Collectors.-Sir W. E. Logan conical Cow Head curved depressed convex Description.-Head Dikelocephalus dorsal furrows dorsal valve edge elevated extremity foramen Formation.-Point Lévis fossils front margin gently concave gently convex genus glabella glabellar furrows greatest width groove height hinge-line inner last whorl Lévis limestone lines in length Locality and Formation.-Point mesial mid-length moderately convex narrowly rounded nearly straight neck furrow neck segment Newfoundland obscure one-third the whole ORTHOCERAS outer Point Rich Port aux Choix posterior margin Potsdam pygidium Quebec group radiating ribs Richardson septa shell side lobes side view Silurian siphuncle slightly slope smooth species specimen spire stolons strongly convex STROPHOMENA suture Table Head tapering transverse trilobites umbilicus umbo umbones upper side ventral margin ventral valve ventricose whole length whole width
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Página 3 - Generic characters. — Turbinate simple or aggregate ; cup deep. The internal structure, so far as can be made out, consists of an inner wall constituting the inner surface of the cup, and an external wall or epitheca enveloping the whole. Between the two walls there are numerous radiating septa, the interseptal spaces being filled with poriferous or cellular tissue.
Página 24 - ... glabella with the fixed cheeks. The neck ' segment is a flat plate inclining upwards and backwards at an angle of about 45°. The neck furrow is well defined all across the whole width of the head, being least distinct in passing over the posterior part of the glabella. Pygidium semioval with a flat border all round abruptly bent down at nearly a right angle. Axis conical, moderately convex, extending the whole length and causing a slight projection in the posterior margin. Side lobes nearly...
Página 6 - ... lines across, and the space between the walls three lines. Of the radiating poriferous septa there are about sixty; they are so irregular that it is only in certain places in finely polished sections that the radiated structure can be detected. On one side, where the specimen is weathered, the structure presents the appearance of a rather compact cellular tissue. The form appears to be elongate conical gradually tapering, the surface marked by wide shallow encircling oblique annulations from...
Página 7 - ... half of the shell, and the others situated one on each side near the cardinal edge. Shell calcareous ; surface concentrically striated, sometimes with thin extended lamellose ridges. In general form, these shells somewhat resemble Obolus, but the arrangement of the muscular impressions is different. In Obolus the two central scars have their smaller extremities directed downwards, and converging towards each other ; but in this genus the arrangement is exactly the reverse.
Página 7 - Muscular impressions in the ventral valve four ; one pair in front of the beak near the middle or in the upper half of the shell, and the others situated one on each side near the cardinal edge. Shell calcareous. Surface concentrically striated, sometimes •with thin extended lamellose ridges.
Página 15 - The front of the head is surrounded by a narrow border which appears to be flat ; there appears to be some evidence of a spine on the neck segment. The pygidium found in the same fragment of stone with one of the specimens of the glabella of this species is in all general characters that of a Bathyurus.
Página 215 - Shell very small, about 1 line in diameter; one valve nearly flat and the other arutely conical. Dorsal valve very gently convex, nearly circular; sides and front margin uniformly rounded; posterior margin very obtusely angulated at the beak, on each side of which a portion of the cardinal edge, equal to one-fourth of the whole width of the shell, is nearly straight; umbo very small; beak apparently depressed to the hinge line and not projecting beyond it; cardinal angles compressed, broadly rounded;...
Página 11 - Description. Ovate or subcircular beaks, obtusely pointed (as seen in the cast), both valves moderately or rather strongly convex. Surface with from eight to ten small rounded ribs which do not reach quite to the beaks. Some of the specimens are proportionally more elongated than others. The front margin appears to be always broadly rounded, and the greatest width at about one-fourth the length from the front margin. Length from four to six lines ; width either equal to or a little less than the...
Página 17 - ... structure of its tube. In the face of these differences, it is somewhat singular to find that the internal casts of the two should be so absolutely undistinguishable except in point of size. Conchicolites presents some resemblances to the genus Salterella of Mr. Billings, defined as consisting of " small, slender, elongateconical tubes, consisting of several hollow cones placed one within another, the last one forming the chamber of habitation of the animal.
Página 17 - Small slender elongate conical tubes, consisting of several hollow cones placed one within another, the last one forming the chamber of habitation of the animal. The cross section of these tubes is circular or subtriangular, and they are either straight or gently curved ; the surface is concentrically or longitudinally striated. I think these fossils, although no doubt allied to Serpulites, sufficiently different therefrom to constitute a distinct genus. Their structure is so compact that they are...