. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. EASTMAN : MYLOSTOMID DENTITION. 215 of the dental apparatus of Mylostoma, his interest in the problem having been aroused by the discovery of a well-preserved skeleton of M. varia- bile, the various parts of which obviously belonged to a single individual. This specimen presented for examination the ilatteued headshield, some half-dozen plates of the abdominal armor, both mandibles, and two pairs of crushing dental plates, all embedded in close proximity to one another in a single block of shale. Tliere were no indica
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. EASTMAN : MYLOSTOMID DENTITION. 215 of the dental apparatus of Mylostoma, his interest in the problem having been aroused by the discovery of a well-preserved skeleton of M. varia- bile, the various parts of which obviously belonged to a single individual. This specimen presented for examination the ilatteued headshield, some half-dozen plates of the abdominal armor, both mandibles, and two pairs of crushing dental plates, all embedded in close proximity to one another in a single block of shale. Tliere were no indications, however, of the presence of a fourth pair of dental elements, corresponding to the so- called " premandibular teeth " of jS'ewberry, and these latter do not enter into Dean's reconstruction. As will be seen from Figure A, which is copied from Dean, the two mandibular rami were found lying nearly parallel to each other in close. FlGUEE B. Restoration of the complete dentition of Mylostoma, based upon the single individual of M. variabile shown in Figure A. The length of the mandibular dental plate is slightly- exaggerated in the outline here shown. X h (After Dean). proximity to the headshield, and at no great distance from the sepa- rated halves of the palatal dentition. The two plates interpreted by Dean as belonging to the right-hand side of the palate are in direct apposition with each other, their contact edges being in remarkably close adjustment. These circumstances, the fact that the two right- hand palatal plates remain together while the corresponding left-hand plates have become separated, and the fact that their opposed edges show almost perfect co-adaptation, are held by Dean to point irresist- ibly to the conclusion that the elements in question have preserved their natural arrangement with respect to each other.^ It is not demon- strated by the author, but merely considered as extremely probable that 1 Dean, B., Palaeontological Notes. Mem. N. Y.
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