DRYDBNIUS INSIGNIS. 101 



1. Duydknius insignis, Traquair. Plate XXII, figs. 5 — 9. 



Drydenius insignis, Traquair. Proc. Roy. Soc. Ediub., vol. xvii, 1890, p. 399 ; 



Trans. Eoy. Soc. Edinb., vol. xl, pt. iii, no. 28 , 

 p. G95. 

 — A. S. Woodward. Cat. Foss. Fishes Brit. Mus., pt. ii, 1891, 

 p. 437. 



Specific Characters. — Attaining a length of four inches or more. Body-scales 

 denticulated posteriorly, anterior covered surface narrow, free surface ganoid, scattered 

 conspicuously with vascular pores. 



Description. — The specimen represented in PI. XXII, fig. 5, can originally have been 

 hardly less than 4f inches in length. Its shape is seen to be fusiform, with the dorsal fin 

 placed over the interval between the ventrals and the anal. As it happens, both ventrals 

 are exhibited in this specimen. 



The cranial roof-bones are covered externally with a proportionally coarse, tortuous 

 striatum, and the ornament of the facial bones is similar in character. The hinder or post- 

 orbital part of the maxilla (fig. 6) forms a short expanded plate, from the middle of the 

 anterior aspect of which (much as in Gonatodus macrolepis) the narrow sub-orbital 

 process extends, so that the tooth-bearing margin is posteriorly bent suddenly down- 

 wards at a very considerable angle. This margin is set, as in Gonatodus, with a single 

 row of proportionally stout cylindro-conical teeth, which do not seem, however, to have 

 the peculiar double flexure characteristic of that genus. The dentary element of the 

 mandible is rather stout and shows on its upper margin a row of similar teeth. The 

 splenial element (figs. 7 and 8) presents a dental armature which I have not seen in any 

 other Palaeoniscid. The bone is narrow, rounded posteriorly, and tapering to a point in 

 front, its upper straight margin (fig. 7) being set with a single row of short, conical, 

 pointed teeth. But the inner or oral aspect (fig. 8) shows an area about the middle, 

 and occupying more than one-third of its length, from which a row of six powerful 

 cylindro-conical teeth arises, behind which are three or four small ones. The large 

 teeth seem disproportionally large for the small size of the fish, and are conspicuous even 

 in the most crushed heads. They are strongly curved, with the convexity on the oral 

 aspect. I rather suspect that the palate is also armed with similar teeth, but I have not 

 been able to see an isolated palate-bone. 



The scales appear rather large for the size of the fish, but show the usual variation 

 of size and form on different parts of the body. Those of the flank (fig. 9) have the 

 posterior border sharply denticulated, and the nearly smooth exposed area is punctated 

 with small vascular openings. Passing backwards the denticulation becomes less 

 marked, then disappears in the scales of the caudal body-prolongation, the punctures 

 likewise tending to become fewer in number. 



