EASTMAN: CATALOG OF FOSSIL FISHES IN CARNEGIE MUSEUM. 367 



Family PYCNODONTIDJ^ 

 " Trunk deeply fusiform or cycloidal. Cranial bones robust, and a median 

 occipital plate separating the parietal elements; facial bones delicate, or wanting; 

 opercular apparatus reduced to a small operculum, large pre-operculum, and not 

 more than two branchiostegal rays; mandibular suspensorium much inclined for- 

 wards and gape of mouth small; teeth prehensile on the premaxilla and dentary, 

 wanting on the maxilla (if this bone be present) and the pterygo-palatine arcade; 

 tritoral on the single vomer and the splenials; all the teeth apparently without 

 vertical successors. Notochord persistent, destitute of ossifications in its sheath. 

 Fin-rays robust, the majority well-spaced and articulated; fulcra absent, except 

 perhaps quite at the base of the caudal fin; dorsal and anal fins more or less extended. 

 Scales rhombic when present, frequently wanting on the whole or part of the caudal 

 region; almost invariably strengthened by the inner rib on their anterior margin 

 and united by a peg-and-socket articulation in connection therewith." (A. S. 

 Woodward, I. c, Ft. Ill, pp. 189-190). 



Genus Microdon Agassiz. 



" Trunk deeply fusiform, often almost discoidal, with a slender abbreviated 

 caudal pedicle. Head and opercular bones ornamented with reticulating rugse 

 and pittings; teeth smooth, sometimes feebly indented in the lateral series; 

 vomerine teeth in five longitudinal series, the inner lateral pairs regularly alternating 

 with the widely spaced median teeth; splenial teeth in four series; the innermost 

 being relatively small ; the second the largest or principal series. Neural and hsemal 

 arches of axial skeleton of trunk not expanding sufficiently to encircle the notochord. 

 Fin-rays robust, closely articulated, and much divided distally. Pelvic fins present; 

 dorsal and anal fins very high and acuminate in front, rapidly becoming low and 

 fringe-like behind, the former occupying at least the hinder half of the back and the 

 latter somewhat shorter, arising more posteriorly; caudal fin forked. Scales orna- 

 mented with reticulating rugse or pittings, and covering only the anterior half of 

 the trunk in advance of the median fins, though sometimes partly extended over 

 the middle of the flank of the caudal region." (A. S. Woodward, I. c, Ft. Ill, pp. 

 221-2). 



The type of the genus is M. elegans Agassiz. 



11. Microdon bernardi (ThioUiere). (Flate LII, figs. 1 and 2.) 

 1854. Pycnodus bernardi ThioUiere. 



Poiss. Foss. Bugey, pt. i, p. 17, with plate. 



