342 TRANSACTIONS, NATURAL HISTORY SOCIETY OF GLASGOW. 
Plate IX., Figs. 13, 14. Scarce; longest specimen found, 2:2 mm. ; 
none is perfect. | 
Polygnathus (Gnathodus ) Mosquensis, Pander, sp. l.c., p. 34, t. 10. 
—This tooth consists of a delicate compressed double-walled plate 
carrying a row of minute triangular flattened denticles on its upper 
edge; at one extremity the walls of the plate diverge so as to 
form unsymmetrical flanges on either side. Viewed from above the 
flange on one side of the central plate is slightly convex and 
ornamented with minute interrupted ridges and furrows. The 
flange on the opposite side is compressed and elevated so as to 
form a crenulated edge which runs nearly parallel with the upper 
margin of the central plate. Viewed from below the flanges are 
concave, and form a spoon-shaped depression with a deeply im- 
pressed line extending from the apex towards the free end of the 
plate. It closely corresponds with Pander’s specimens from the 
mountain limestone of Moscow. : 
[In Scotland it occurs at Glencart, Linn Spout, Monkcastle, 
Stacklawhill, Robroyston, Birkhead, Cunningham Baidland, Law, 
and Glenbuck. Plate IX., Figs. 2, 3,4. Comparatively frequent ; 
1-2 to 20 mm. in length. ] 
Polygnathus navicula, Hinde, new species. Plate IX., Fig. 5. 
—The basal portion of the tooth is triangular in outline when 
viewed laterally,its upper surface is a flattened plate, transversely 
striated, and with a median furrow. At one end there rises at 
right angles to the plate a thin crest with four or five saw-like 
denticles. This tooth is of the same character as the peculiar den- 
ticulated plates from the Devonian of Canada which are figured 
in the Quar. Jour. Geol. Soc. for 1879, pl. 17, £. 8-11, but differs 
in the form and disposition of the central crest. [From Ponniel 
Water, near Douglas. Only one specimen found ; 1-7 mm. in 
length. | 
Polygnathus (Centrodus) convexus, Pander, Mon., p. 31, t. 24, 
f. 4.Base of the tooth narrow and strongly curved, with a 
series of from 4 to 7 large, compressed, pointed denticles radiat- 
ing from its upper margin. Sometimes minute denticles are 
intercalated between the larger. Pander’s specimens are from 
the Lower Carboniferous of Tula. [In Scotland it occurs at 
Glencart, Monkcastle, Law, and Auchenskeith. Plate IX., Figs. 
6, 7, 8. Specimens measure from *8 to 2 mm. in length. | 

