﻿174 Revieivs — Poussin 8f Renard — Belgium ^ the Ardennes. 



from the other two," And that "the peculiar form and arrangement 

 of the teeth in the first of these render necessary the institution of 

 a new genus, to which I have given the name of Gonatodus." He, 

 however, preserves Agassiz's name of punctatus for tlie species ; but 

 redescribing it from original and careful observation of the more 

 complete material at his command. He further observes that "the 

 peculiar dentition of Gonatodus was, however, first correctly de- 

 scribed by Mr. R. Walker, in a fish from the oil shales of Pitcorthie, 

 Fifeshire, to which he gave the name of AmbJypterus ancono- 

 (Bchmodus." And that " Mr. Walker's fish undoubtedly belongs to 

 the same genus, and may possibly be the same with G. punctatus.'' 



Gonatodus macrolepis, Traq., is a new species, ranging in length 

 from four to seven inches, and occurs in the Blackband Ironstone. 

 The configuration of the bones of the head, as far as they can be 

 defined (for in the specimens examined they are all more or less 

 crushed and broken), and their sculpturing, and also the configuration 

 of the teeth are essentially the- same as in the preceding species ; but 

 the scales on the anterior portion of the body are considerably 

 larger than in G. punctatus, and as in that species the surfaces are 

 brilliantly polished, and devoid of ornamentation, and their posterior 

 margins are finely denticulated. 



Ample and clear as are the descriptions, we cannot conclude with- 

 out expressing regret that they have not been supplemented by good 

 figures of the specimens upon which the speoies have been founded. 



W^ D. 



Y. — Memoire sub les Caraotekes Mineralogiques et Strati- 



GRAPHIQUES DES EOGHES DITES PlUTONIENNES DE LA BeLGIQUE. 



ET DE l'Ardenne Fran(jaise. By Professors C. de la Valleb 

 Poussin and A. Eenakd. 4to, pp. 264, and 7 plates. (Brussels, 

 1876.) 



DE SAQSSURE declared that mountains were not to be studied 

 with the microscope. What would that venerable father of 

 geology think could he see the "slicing" of rocks which is now 

 going on all over Europe I It was the custom, not so very long ago, 

 for geologists to be content, for descriptive purposes, with a small 

 stock of words wide and rather vague in meaning— of which "trap " 

 is a worthy example — words which bound one to very little or 

 nothing. A hand-lens to be used in the field was the only auxiliary 

 thought of in determining the lithological characters of rocks. Now 

 all is changed, the geologist trembles as he hazards a name for the 

 specimen he collects, for he knows not how wrong he may be proved 

 to be by that newly-arisen votary of science — the Micro-petrologist. 

 The rock-nomenclature of his youth is gone, he knows nothing of, 

 and finds it hard indeed to learn the meaning of " fluidal structure," 

 "devitrification," " globulites," "belonites," or "margarites," and 

 the result is that he, as a rule, gives up the attempt, and relies, for 

 the determination of his rock-specimens, on the knowledge of those 

 who have made micro-lithology their special study. In England the 

 number of these specialists is small but increasing, headed as they 



