. Bulletins of American paleontology. Alaskan ammonites. Pi. II: Westermann 57 u 30 - 20 - 10 -. D (mm) Text-fig. 20. — Scatter for relative umbilical width (U:D) of Pseudolio- ccras costisiriatum, n. sp. (circles, H = holotype) and P. madintocki ivhitcavesi (White) (dots with visually drawn central line). Note the narrower umbilicus of the new species. ly, the vimbilical slope heightens and the margin raises to form an increasingly strong umbilical edge; the maximal whorl width lies approximately in the middle of the flattened sides; the venter be- comes distinctly tabvilate-unicarinate at ab
. Bulletins of American paleontology. Alaskan ammonites. Pi. II: Westermann 57 u 30 - 20 - 10 -. D (mm) Text-fig. 20. — Scatter for relative umbilical width (U:D) of Pseudolio- ccras costisiriatum, n. sp. (circles, H = holotype) and P. madintocki ivhitcavesi (White) (dots with visually drawn central line). Note the narrower umbilicus of the new species. ly, the vimbilical slope heightens and the margin raises to form an increasingly strong umbilical edge; the maximal whorl width lies approximately in the middle of the flattened sides; the venter be- comes distinctly tabvilate-unicarinate at about 25 mm diameter and sometimes even somewhat bisulcate on the mature phragmocone; the hollow-floored keel is not strong but well defined. The ornament consists of blunt typically falcate principal costae tending to become obsolete on the inner flank. The flattened outer costae are striated superficially, often appearing as costellae compounds, and sometimes weakly fasciculate on the inner whorls. The falcate striae or costellae bundles are also present on the in- ternal mold of the relatively large holotype, particularly on the shoulders where they appear as faint intercalated secondaries, and also appear irregularly on the middle of the sides. A single con- cave outer rib is sometimes intercalated. The septal suture is of moderate complexity and resembles that of other Pseudolioceras. Comparison. — P. costistriatum somewhat resembles P. maclin- tocki (Haughton) and particularly the subspecies P. m. whiteavesi (White) from which it is distinguished by the narrower umbilicus, the tabulate-unicarinate venter, and the falcate striae or Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Paleontological Research Institution (Ithaca, N. Y. ); Columbia University. Ithaca, N. Y. , Paleontological Rese
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