44 Dipterians. 



had not true scales imbricated on the body, but only large 

 plates covering the head and nape. There is nothing hitherto, 

 it is true, to prove this supposition, but the fact is neveHhe- 

 less curious, that along with the great quantity of large 

 slabs of Asterolepis and Bothriolepis which characterize 

 certain formations, we have never found true scales which 

 can be assigned to them. I point out this fact to the atten- 

 tion of geologists ; for nothing is often more instructive than 

 the mode in which fossils are associated, particularly when 

 the remains belong to animals whose size and the softness 

 of the skeleton have prevented them being preserved entire. 

 But it is necessary to employ the greatest circumspection in 

 appropriations of this nature before drawing conclusions from 

 them : for too frequently these results are transmitted from 

 one author to another, and sometimes still continue to pass 

 for truths, when the state of the facts has been modified. 

 The beds of the old red sandstone, it is true, are not very 

 favourable to researches of this nature, for the fossils not 

 forming in them the nuclei of rounded masses, the remains 

 are dispersed and mingled in such a manner, that we often 

 find in the same morsel of indurated matter the remains of 

 many genera entirely different. 



The family of the Dipterians, like that of the Cephalaspi- 

 des, is entirely confined to the strata of the old red sandstone. 

 Here the affinities to the Sauroides are so evident, that I 

 have thought it necessary to give up the opinion to which I 

 for some time adhered, of regarding them as a separate 

 family. The scales are the same, and the teeth approximate 

 in every respect, in the genera Osteolepis and Diplopterus, to 

 the eminently carnivorous type of the Sauroides with insu- 

 lated incisive teeth. I have provisionally placed in this 

 family the genus Glyptopomes, which, in the sculpture of its 

 scales, makes a near approach to the Platygnathes of the 

 family Celacanthes, but recedes from it, on the other hand, 

 in the form and arrangement of its scales, which are evi- 

 dently only in juxtaposition and cut lozenge-shape. It would 

 be very interesting to know how the position of this genus 

 will be ultimately fixed ; whether it be necessary, from the 

 arrangement of its fins, to place it definitively among the 



