. Bulletins of American paleontology. . B Text-figure of the cooperculum of Spondylospira lewesensis {Lees, 1934). A, thin-section, x 12, mm dorsad of ventral beak, parallel to commissural plane, of ventral valve, GSC 69374D (chorotype, from loc. 30), showing ridged interarea, dental plates, and median septum fonning anterior portion of the spondylium, deltidial plates, and severely distorted cooperculum. Note that the shell structure of all internal portions of the shell is fibrous and laminar, while the cooperculum is clearly punctate externally and laminar internally, as is th
. Bulletins of American paleontology. . B Text-figure of the cooperculum of Spondylospira lewesensis {Lees, 1934). A, thin-section, x 12, mm dorsad of ventral beak, parallel to commissural plane, of ventral valve, GSC 69374D (chorotype, from loc. 30), showing ridged interarea, dental plates, and median septum fonning anterior portion of the spondylium, deltidial plates, and severely distorted cooperculum. Note that the shell structure of all internal portions of the shell is fibrous and laminar, while the cooperculum is clearly punctate externally and laminar internally, as is the ventral valve (shown only as fragment at extreme upper left of figure), except for the ndged portion of the interarea; B, postenor view, x , of portion of ventral valve, GSC 69373 (chorotype, from loc. 30), showing punctate surface of cooperculum, its irregular mesial suture (ticks mark top and bottom), and the lateral rugae and vertical furrows on its surface, [enlargement, upside down, of PI. 9, fig. 21].. 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 Research Institution [etc. ]
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