Geological Society of London. 279 



I^EI^OI^TS J^IsTID I^iaOOEIEnDIIsrOS. 



Geological Society of London. — T. — April 5, 1871. — Professor 

 Morris, Vice-President, in the Chair. The following communications 

 were read : — 1. " On a new ChimEeroid Fish from the Lias of Lyme 

 Eegis." By Sir Philip Grey Egerton, Bart, M.P., F.E.S., V.P.G.S. 



This fish, for which the author proposed the name of IscJiyodus 

 orthorJimiis, was represented by a specimen showing the anterior 

 structures imbedded in a slab of Lias. It exhibited the charac- 

 teristic dental apparatus of the Chimasroids, surrounded with sha- 

 green, a very large prelabial appendage six inches long, and termi- 

 nating in a hook abruptly turned downwards, and a process which 

 the author regarded as representing the well-known rostral appen- 

 dage of the male Chimaeroid, but in this case attaining a length of 

 6^ inches, and covered more or less thickly with tubercles, bearing 

 recurved central spines somewhat tooth- like in their aspect. This 

 appendage is attached to the head by a rounded condyle, received 

 into a hollow in the frontal cartilage. The dorsal spine, which 

 measured 6 inches in length, was articulated by a rounded surface 

 to a strong cartilaginous plate projecting upwards from the noto- 

 chordal axis, and was thus rendered capable of a considerable amount 

 of motion in a vertical plane. This structure also occurred in 

 Callorhynchus and CJiimcBra. 



Discussion. — Dr. G'linther commented on the interest of this discovery, as in no 

 other Sharks is the same articulation of the dorsal spine as that described in the 

 paper to be found. He inquired whether the granulated plate supposed to be dorsal 

 might not be a part of the armature of the lateral line, as in Sturgeons. He thought 

 that the Chimseroids would eventually prove to be intermediate between the Ganoid 

 and Shark types, and that all belonged to one sub-class. 



Mr. Gwyn Jeffreys inquired what other remains wer.e found with these fishes, such 

 as might represent the food, molluscan or otherwise, on which they lived. 



Sir P. Egerton replied that there was no deficiency of pabulum for any kind of fish 

 in the sea represented by the Lias of Lyme Eegis. He also made some remarks on 

 another somewhat similar specimen in his own museum. The plate referred to by 

 Dr. Gunther, he stated, was symmetrical, and not like the lateral plates on the 

 Sturgeon, which are unsymmetrical. He therefore thought it dorsal. 



2. " On the Tertiary Volcanic Rocks of the British Islands." By 

 Archibald Geikie, Esq., F.E.S., F.G.S., Director of the Geological 

 Survey of Scotland, and Professor of Geology and Mineralogy in 

 the University of Edinburgh. (First paper.) 



In this communication the author gave the first of a series of 

 papers which he proposes to lay before the Society upon the volcanic 

 rocks of Britain of later date than the Chalk. In a general intro- 

 duction to the whole subject, he pointed out the area occupied by the 

 rocks, showing that they are chiefly developed along the broad tract 

 which extends from the south of Antrim, between the chain of the 

 Outer Hebrides and the mainland of Scotland, up into the Faroe 

 Islands, and even to Iceland. The nomenclature of the rocks was 

 discussed, and the following arrangement was proposed : — 



