from the Shales of the Northumherland Coal-field. 359 



must be taken to qualify it. They are, — " Mais les dents sont si 

 excessivement petites qu'il est tr^s-rare de pouvoir les distin- 

 guer." From this it is pretty evident that this distinguished 

 naturalist knew very little about the matter. Succeeding 

 writers, however, appear to have rested satisfied with this 

 description. Mr. Binney, indeed, so long ago as 1841* figured 

 the jaw of Palmoniscus Egertoni^ showing a row of large, co- 

 nical, sharp-pointed teeth, as well as a few of the small ex- 

 ternal ones. He says that the jaw is " armed with sharp 

 conical teeth of a nearly uniform size, inclining from the 

 front." This communication, however, has been unfortunately 

 overlooked. 



The teeth of these jaws are not " en brosse," neither are 

 they of that feeble " villiform " structure so much insisted on 

 of late. They are disposed in two distinct rows, one within 

 the other, much in the same fashion as in Megalichthys and 

 Uhizodopsis^ but still much more like that which obtains in 

 Pygopterus^ in which the teeth are likewise arranged in two 

 rows — one being of large laniary teeth, the other of small 

 external ones. And, according to M. Agassiz, they do not in 

 this genus form " une .brosse ou rape comme les dents du Fo- 

 lyterus^ The inner row in Palceoniscus (PI. XV. figs. 3, 4, 5) 

 is composed of a few comparatively large, curved, sharp-pointed 

 conical teeth, which are placed at some little distance apart 

 from each other. In the outer row the teeth are numerous, 

 small, conical, and pointed, occasionally crowded, and in some 

 species apparently not quite in regular order. 



It is this outer row of comparatively small teeth that aj)pears 

 to have been seen and described by M. Agassiz, the inner row 

 of laniary teeth having escaped his observation. Nor is it any 

 wonder that such a matter of detail should have been over- 

 looked by this naturalist ; and, indeed, many such omissions 

 are found in the great work alluded to. But when we con- 

 sider the novelty and vastness of the matter before him, and 

 especially that the bent of his mind was directed mainly to the 

 larger problems of his subject, the only marvel is that such 

 blunders are not more numerous. The laniary teeth are 

 very frequently concealed in the matrix ; and when the jaw 

 is in its natural position, they are liable to be obscured by 

 the extenial row, which stands up on an elevated ridge of the 

 alveolar margin. 



The laniary teeth vary in number in the different species, 

 and probably, in a limited degree, even in the same species : 

 but this is difficult to determine ; for it rarely happens that the 



* Trans. Manchester Geol. Soc. vol. i. p. 107, pi. 5. fig. 12 (1841). 



