No. 379. ] DEVONIAN PTYCTODONTIDE. 487 
of the upper dental plate is remarkably straight and sharp. 
None of the specimens appear to have exceeded 5 cm. in 
length. 
(4) R. rostratus, sp. nov. (Figs. 41, 44-47). — The char- 
acters of this species, as determined from nearly a score of 
dental plates in the Schultze Collection in the Museum of 
Comparative Zoology, are as follows: Lower dental punes 
attaining a length of about 6 cm. and a height of about 2 cm. 
perfectly straight, laterally compressed, smooth and glisténiug 
externally, or with only very fine concentric sttiæ. Superior 
margin semicircular or nearly so, being concave upward ; front 
margin regularly convex and terminating above in a sharp 
projecting beak. Cutting edge occupying nearly the entire 
superior margin, very sharp, and beveled on the inner face 
through wear. Inner face slightly thickened at the symphysis, 
but never wider than 0.5 cm., otherwise plane like the outer. 
_ A peculiar lanceolate or tongue-shaped cavity, having the apex 
directed superiorly, occurs on the lower half of the symphysial 
area; its roughened surface suggests that it served for the 
reception of ligaments which held the two rami together at 
the symphysis. Upper dental plates unknown. 
Two rather imperfect specimens in the Schultze Collection 
are interesting from having been figured by Hermann von 
Meyer,! under the mistaken impression that they were swimming 
appendages of his so-called ‘“ Physichthys Honinghausi.” All 
the originals on which his descriptions were based are preserved 
in the Cambridge Museum, and obviously belong to the three 
genera, Macropetalichthys, Pterichthys, and Rhynchodus, as 
was first pointed out by A. S. Woodward ? a few years ago. 
_ This species is known at present only from the Eifel Devo- 
nian, the Cambridge specimens having been found at Pelm, 
Gerolstein, and Berndorf. 
(5) R. major, sp. nov. (Fig. 42). — This form accompanies 
the preceding in the Eifel Devonian, the typical locality being 
Prüm. Complete dental plates have not been recovered as yet, 
1 Meyer, von, H. Ta Höninghausi, etc., Paleontographica, vol. iv 
(1856), Pl. XV, Figs 
* Geol. Magazine, Li ae (1890), p- 459- 
