Powrie — On the Genus Cheirolepis. 



149 



position of the whole cannot be accurately ascertained. The collec- 

 tion of the late Mr. Patrick Duff, of Elgin, which, since his death, 

 has passed into my hands, contains one or two very fine specimens 

 of Cheirolepis Cummingice, in one of which the fish is laid on its back, 

 the ventral surface being thus exposed; and, although in it the plates 

 covering the under portion of the head are not perfectly preserved, 

 yet they appear to me sufficiently so to show two principal, and a 

 space which may have been occupied by lateral, jugular plates (See 

 Woodcut, Fig. 1); the lateral plates are not sufficiently preserved in 

 any of my specimens of this species to admit of restoration, but a 

 specimen from Gamrie, in my cabinet, exhibiting a number of the 

 head plates of Cheirolepis uragus, has the lower jaw with a number of 

 elongated narrow plates proceeding from its under margin, much 

 resembling those given by Agassiz in his figure of this species, 

 (" Poiss. Foss.," vol. ii. plate 1 c, fig. 1.) These I presume are what he 

 describes as Branchiostegal rays, but which, I have little doubt, cor- 

 respond to the lateral jugular plates, not uncommon in ganoid 

 fishes (Fig. 2). I have, also, introduced these in Fig. 1, which is a 



Fig. 2. — Diagram of Head-plates of Cheirolepis (side view). 



tolerably correct copy of the under head plates, as exhibited in the 

 first mentioned specimen. The numbers are the same in both 

 figures. 



The upper jaw (1), as described by Huxley, is a large bone, 

 having its posterior superior margin rounded, its posterior half in- 

 creasing in depth anteriorly, when it suddenly narrows, exhibiting a 

 concavity, affording space for the orbit, and, seemingly, a number of 

 orbital ossicles, and terminating anteriorly in an elongated narrow 

 bone, somewhat bent upwards, the under margin being slightly con- 

 cave posteriorly, and exhibiting an equally slight concavity forwards ; 

 this bone, however, seems to me to have consisted of the maxilla, 

 and likewise of a supra-temporal bone, completely anchylosed to 

 the maxilla. The lower jaw (2) is moderately stout posterior y, 



