Administrative Report and Economic and Geological Papers

Administrative Report and Economic and Geological Papers

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1917 edition. Excerpt: ... than long, the greatest width anterior to the middle; the front margin straight or very slightly rounded, not extended in the middle portion. Ventral valve convex in the umbonal region becoming flattened a little behind the middle, where it gradually becomes depressed into a mesial sinus which broadens and deepens anteriorly, and is occupied by three plications. Beak much elevated, acute, not incurved. Dorsal valve broadly triangular, convex, the median area slightly depressed in the umbonal region, but in the anterior half of the shell it becomes elevated into a low fold which bears four subequal plications. Beak strongly incurved beneath that of the ventral valve. Surface of dorsal valve marked by 14 subangular plications, of which 4 are slightly elevated into a fold near the front margin. Ventral valve bearing 15 plications, of which 3 are depressed into a shallow sinus. Around the margins the extensions of the grooves on one valve fit into corresponding angular notches below the ribs of the opposite valve. A few concentric lines are present near the margins of both valves. _ The dimensions arc: length, 9 to 10 mm.; width, 10 to 11 mm.; thickness, 4.5 mm. In some features this species resembles Rhynchonella? janea of the Edgewood formation, from which it differs in its smaller size, in its lower and less angular plications, and in the less incurved beak of the ventral valve. The species is not rare in the Girardeau limestone, near Thebes, Illinois. Camarotoechia? festinata n.sp. (Plate III, figures 24, 25 and 26) Shells resemble small individuals of Camarotoechia? scobina, from the Brassfield of Ohio, in their triangular outline; strong angular plications; and in having the two exterior plications of the fold narrower and less...show more

Product details

  • Paperback | 62 pages
  • 189 x 246 x 3mm | 127g
  • Rarebooksclub.com
  • United States
  • English
  • black & white illustrations
  • 1236739078
  • 9781236739070