Neithea altana Kniker, 1919
KNIKER, H. T. 1919. Comanchean and Cretaceous Pectinidae of Texas. Bulletin of the University of Texas, 1817: 1-56, pls. 1-10 [p. 36, pl. 7, figs. 1-3]
1919 Neithea altana Kniker, 1919
H. T. Kniker, 1919, plate 7.
|
«Description.— Shell medium, short and broad (?), subtrigonal; ventral margin gently rounded; ears imperfect, but appear to be prominent.
Right valve moderately convex, rounded. The writer has not been able to find perfect specimens of this form, but it is so different from the other Georgetown Neitheas that it will be described and figured. As in the other species of this group, there are sixteen strong, radiating ribs on the right valve. But, contrary to the ordinary arrangement, every third rib is raised so slightly that it can be detected only with difficulty. Furthermore, the ribs are high and narrow. Allare flattened on top and equal in width. They are practically twice as wide as the interspaces. On account of this, and because they are narrow, they seem to be crowded in the umbonal region and, consequently, appear to be sharp, and not flattened on top. However, near the base of the shell they are distinctly flattened. A few secondary ribs are sometimes found on the areas. The lines of growth are indistinct. The left valve is missing. Affinities.— This species is easily distinguished from N. subalpina by its ribs, which are practically equal in height and width, and are distinctly flattened on top. Number of specimens: About 15. Occurrence : Georgetown Limestone, Austin, Texas.» HEDWIG THUSNELDA KNIKER, 1919
|