Diphyodus longirostris

Lambe L. M., 1902, New genera and species from the Belly River Series (mid-Cretaceous), Geological Survey of Canada Contributions to Canadian Palaeontology 3, pp. 25-81 : 30

Diphyodus longirostris . Sp. nov.

Plate XV., figs. 18 and 19 .

The bone figured on the above plate affords evidence of the complete coalescence of the premaxillaj in a fish to form a long, slender, snout armed with teeth that succeeded each other in a regular alternating manner. These characters have suggested the names of the genus and species proposed.

The specimen is in the form of a comparatively thick plate bent, on itself, so as to be U-shaped in transverse section; it is imperfect at both ends, is 23 mm. long, tapers slightly toward the from, and is 4 mm. broad posteriorly and 3'5 mm. broad at its anterior end. There is no evidence of a median longitudinal suture. The sides of the hollow semi-cylin- der thus formed, are slightly over 1 mm. thick, but the thickness of the basal part is over 2 mm. On the flattened upper surface of the two sides, are preserved, circular bases of teeth, anchylosed to the bone, that appear as raised circles, averaging '80 mm. in diameter and aboixt 2 mm. apart from centre to centre. On the right side there are nine teeth represented at equal intervals, but on the left side, although there were a like number of teeth, the interspaces are not so regular. Shallow subquadrangular depressions, varying in number from one to three, according to the length of the interspace, occur between the tooth-bases. Each depression represents the former position of a tooth that has fallen out or has been broken off.

A circle of minute pits or foramina surrounds each tooth-base; similar but less regular pits occur in the intervening depresssions and a few are observed within the tooth-bases themseh'es. Two tubular canals, placed side by side, above the centre of the base, pierce the bone longitudinally throughout its length. The bottom of the median groove between the two rows of teeth has an undulating surface. The sides and rounded base of the bone are smooth and show irregular longitudinal lines of small pit-like markings. One of the tooth-bases at the posterior end is decidedly subquadrangular or oval in shape with its larger diameter transverse.

Two or three fragments present the same characteristics of structure.

Belly River series, Red Deer rive:, 1901.

Figures

PLATE V Fig. 1. Trachodon (Pteropelyx) marginatus Lainbe. right inaxillarv bone. external view: reduced one- 1¬¬1. ¢_ um» 7.1-.. -..De Fig. 2. The same, internal view. Fig. 3. The same, superior view. a, facet for jugal; b, facet for palatine.

PLATE X. Fig. 1. Trachodon (Pteropelyx) marginatus, Lambe, left pubis, external view; one-third the natural size. (Provisionally associated with T. marginatus). Page 74. Fig. Ê. Trachodon (Pteropelyx) marginatus, left ischium, external view, " one-fifth the natural size. (Provisionaily associated with T. marginatus). Page 75. i, iliac facet; b, acetabular border; g, ischiac facet; ÍL, postpubic process; p, pubic facet; pp, postpubie facet; j, flange.