78 REPORT 1860. 



body. It is distinguishable also from Acanthodes Peacki, a new species discovered 

 last year by Mr. Peach in the Caithness flags, by the form of the spines, the pectoral 

 spines in the latter being straight, and the dorsal and anal spines curved. 



Photographs of Fishes, from Farnell in Fifeshire, were exhibited by Mr. W. Rogers, 

 of Montrose. 



On a Neio Form of Ichthyolite discovered by Mr. Peach. 

 By Sir Philip Egerton, Bart, M.P., F.R.S. 



This fossil fish, discovered by Mr. Peach in the Caithness flagstones, is chiefly re- 

 markable for the structure of the fins. The dorsal and anal fins are supported upon 

 three interspinous bones in each organ, from which the fin-rays spread in tufts. A 

 similar structure prevails in the caudal fin. It is nearly allied to Dipterus, and pro- 

 bably belonged to the Coelacanthoid family. The name Tristichopterus alatus has 

 reference to the peculiar structure characteristic of the genus. 



On Circular Chains in the Savoy Alps. 

 By M. A. Favre, Professor at the Academy of Geneva. 



The object of this memoir is to describe the peculiar structure of the mountain 

 chains in Savoy, on the left bank of the river Arve. 



This region may be divided into several districts, which, in passing from Mont 

 Saleve to Mont Blanc, are as follows : (1) the Tertiary, (2) the Cretaceous, (3) the 

 Jurassic, and (4) the district of crystalline rocks. M. Favre treats of the second of 

 these, in which the mountain chains surmounted by precipitous peaks are composed in 

 great part of cretaceous rocks. This district is about 49 kilometres long from the 

 river Arve to the lake of Annecy, by 24 broad. The loftiest mountain attains the 

 height of 2760 metres above the sea-level, and there are several other summits be- 

 tween 2300 and 2400 metres high. The geological formations which constitute this 

 district are, — 1. the Jurassic which occupy a very limited space ; 2. the Neocomian; 

 3. the Urgonian, which forms enormous escarpments, and constitutes the crest of the 

 mountains; 4. the green sandstone; 5. the chalk; 6. the nummulite limestone ; 7. 

 the alpine macigno, which at its base contains various nutria with fish scales, and 

 above marls and sandstones associated with the Taviglianas freestone which is a 

 species of volcanic cinder. 



One of the valleys of this district, that namely of Thones on Grand Bornant, is a 

 longitudinal valley ;" the others are transverse valleys watered by rivers arranged almost 

 like the radii of a circle. This peculiarity in the direction of these rivers depends on 

 that of the mountain chains ; for the rivers in general cut the chain perpendicularly 

 to their axes, and with the exception of Mont Charvin a la Pointe Percee, all the 

 mountain chains of this district, and especially those on the borders, are in the shape 

 of a quadrant, and lie in every direction that can be found in a quadrant. It is to 

 these chains that M. Favre has given the name of circular chains. 



Mountain chains have long been remarked whose axes are more or less undulatory, 

 others separating from a common trunk like the branches of a tree ; strata, moreover, 

 have been observed that rise to the surface of the ground in the form of the bottom 

 of a boat ; and the opposite phenomenon has likewise been observed, that namely of a 

 mountain chain in the form of a vault or half cylinder sinking so as to disappear in 

 the plain ; but M. Favre is of opinion that the fact to which he has called attention is 

 different from any of these, insomuch as it refers to entire chains, which are not only 

 curved, but curved to such a degree that their extremities are at right angles to each 

 other. 



M. Favre concludes his essay by calling attention to the fact that the chains of the 

 Alps display the closest orographical resemblances to those of the Jura, which are 

 now well known. Although the displacement of the soil is much greater in the Alps 

 than in the Jura, in both are found groups either entire or broken, which in the latter 

 case disclose in their interior, one, two, or three of the strata below that which forms 

 their crest ; in both are found combes, ravines, and valleys of the same form. M. 

 Favre believes that the identity of these forms leads to the conclusion that the eleva- 

 tion of the Alps and the Jura is due to causes of the same nature. 



