. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology; Zoology. EASTMAN : STRUCTURE AND RELATIONS OF MYLOSTOMA. 13 Neoceratodus the median series is reduced to one anterior element, covering the pineal and rostral (or ethmoid) regions, and one elongated posterior element (M 0), these two plates being suturally united with each other, and excluding the paired central elements from contact along the median line. Nevertheless in Protopterus the plates corre- sponding to the centrals are actually in apposition along the median. Fig. B. — Neoceratodus forsteri (Krefft). Dorsal
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology; Zoology. EASTMAN : STRUCTURE AND RELATIONS OF MYLOSTOMA. 13 Neoceratodus the median series is reduced to one anterior element, covering the pineal and rostral (or ethmoid) regions, and one elongated posterior element (M 0), these two plates being suturally united with each other, and excluding the paired central elements from contact along the median line. Nevertheless in Protopterus the plates corre- sponding to the centrals are actually in apposition along the median. Fig. B. — Neoceratodus forsteri (Krefft). Dorsal aspect of cranial roof, drawn as if flattened out, and dermal plates lettered to correspond with those in Dinichthys. Cartilag- inous elements (PO) dotted; suborbitals omitted. From a specimen in M. C. Z., x £. line for a certain distance anteriorly, and in Homosteus the median occipital is relatively more elongated than in Neoceratodus. The latter shows an abrupt downward deflection of the bone-substance along a portion of the posterior margin of the cranial roof. Like conditions are found in Macropetalichthys, even more conspicuously developed. Macropetalichthys and Homosteus both have the external occipital greatly enlarged at the expense of the central elements. Neoceratodus, on the other hand, has the centrals enlarged at the expense of the external occipitals (Fig. B, EO). In Ceratodus sturii these plates are more nearly as in Dinichthys. The remaining elements of the cranial roof in Neoceratodus are easily. 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 Harvard University. Museum of Comparative Zoology. Cambridge, Mass. : The Museum
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