﻿POSITION OF THE PAL^EONISCIDtE. 



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those more external ; minute teeth are also seen on the edge of the splenial. Though hardly 

 "en brosse," the appearance of the teeth (PI. I, figs. 3, 4, and 12) sufficiently accounts for 

 Agassiz's use of that expression in characterising the genus ; unfortunately, however, he 

 included in Palceoniscus several Carboniferous forms in which more pronounced laniaries 

 are conspicuously present. In like manner the smooth-scaled species of his genus 

 Amblypterus (A. latus, lateralis), to which the name has been very properly restricted by 

 Troschel, possess very minute, slender teeth, showing no trace of interspersed laniaries, 

 and much more than in Palceoniscus meriting the title of " en brosse'' But in Bhabdolepis, 

 Troschel (e. y., R. macropterus = Amblypterus macropterus, Agassiz), in Elonichthys, Giebel, 

 including several species referred to Palceoniscus by Agassiz (U. Egertoni, striolatus, 

 Bobisoni), in Acrolepis, Nematoptycltius, Cycloptychius, Bhadinichtkys, Owyynat/ius, 

 Pyyopterus, &c, there exists a set of strong and powerful conical or laniary teeth placed 

 in a row internal to an outer series of closely and somewhat irregularly placed smaller 

 ones, with which they appear to some extent interspersed. In Cheirolepis the larger 

 teeth, proportionately not so large as in some other genera, are placed in a close and 

 even row along the margin of the jaw, while external to them is a series of numerous 

 and more irregularly placed teeth of very minute dimensions. In Cosmoptychius striatus 

 {Amblypterus striatus, Agass.) the dentition resembles that of Cheirolepis in that the 

 laniaries are of no great size and placed tolerably closely, but outside them we still find 

 a distinct outer series of half the size of the others or less. In the immense majority of 

 Palceoniscidce, then, the arrangement of the teeth displays the character laid down by 

 Agassiz as distinctive of the " Sauroides " and " Celacanthes." And in point of fact it 

 is clear enough that the only difference in dentition between Palceoniscus and such a form 

 as Pyyopterus is, that in the latter certain teeth occupying a certain position in the jaw 

 are more largely developed — a difference it may be of generic, but hardly of family, 

 importance. 



In some forms, however, the dentition is a little peculiar. In Gonatodus punctatus 

 (Amblypterus punctatus, Agassiz) the teeth are in one row, closely set, of moderate and 

 uniform size, and with no trace, as far as can be seen, either of larger teeth internal, or of 

 smaller ones external to them. Each tooth is first bent outwards at an obtuse angle, the apex 

 being then sharply curved so as to point upwards. This unusual form of tooth was first 

 described by Mr. R. Walker in a fish from the Eifeshire Calciferous Sandstone series, to 

 which he gave the name of Amblypterus anconocec/anodus. 1 In the lower jaw he described 

 the teeth as being placed alternately, one close to the outside margin, the one next to it being 

 " fully half its own thickness further in, and so on the whole length of the bone." And 

 in the curious little fish from North Staffordshire for which I propose the name of 

 Microconodus Molyneuxi, the teeth are also apparently in one row, of uniform size, 

 and bluntly conical, though not showing the peculiar flexures of Gonatodus. 



1 "On a new species of Amblypterus, and other fossil Fish Remains from Pitcorthie, Fife," ' Trans. 

 Edinb. Geol. Soc.,' vol. ii, pt. i (1872;, pp. 119—124. 



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