. Bulletins of American paleontology. Mexican ammonites: Verma & Westermann 175. Text-fig. 14. — A Cross section of Aulacosphinc- toides lauri (Aguilera), phragmocone, McM - J 1509/23, XI- B. Cross section of Subdichotomoceras, n. sp. aff. S. inversum Spath, macroconch [$] phragmocone, McM - J 1506/17, inent secondaries at 2/3 whorl height. Intercalatories are also com- mon. The secondaries continue prominently across the narrow venter. The ribs become blunt toward the end of the phragmo- cone. Remarks. — Because our collection of several thousand am- monites from Sierra Catorce cont
. Bulletins of American paleontology. Mexican ammonites: Verma & Westermann 175. Text-fig. 14. — A Cross section of Aulacosphinc- toides lauri (Aguilera), phragmocone, McM - J 1509/23, XI- B. Cross section of Subdichotomoceras, n. sp. aff. S. inversum Spath, macroconch [$] phragmocone, McM - J 1506/17, inent secondaries at 2/3 whorl height. Intercalatories are also com- mon. The secondaries continue prominently across the narrow venter. The ribs become blunt toward the end of the phragmo- cone. Remarks. — Because our collection of several thousand am- monites from Sierra Catorce contains only three specimens of Mazapilites, this genus appears to be extremely rare in this area. None of the syntypes of M. mexicanus could be found among the type collections in Mexico. Fortunately, however the plastotype of one of Aguilera's syntypes (1895, pi. VII, fig. 1) is available at the United States National Museum (USNM 103295). M. mexicanus resembles the type species M. sym^onensis Burckhardt (1919-21, p. 4, pi. 1, fig. 4, 5) but is somewhat more compressed and has a more narrow venter. M. crassicostatus Burckhardt (1919-21, p. 7, pi. 2, figs. 1-4, 6, 7, 10) is much more coarsely ribbed and, like most other ill-defined species of Mazapilites described by Burckhardt, has a broader 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. ]
Size: 1343px × 1860px
Photo credit: © Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorpaleontologicalresearchinstitutionit, bookcentury1900
