518 British Association Reports. 
of Reswallie, Forfar, Mr. Lightbody, and Mr. Humphrey Salwey ; 
and had also had access to the material collected by Professor 
Huxley. His investigations had led him to conclude that there 
were five British species of Cephalaspis, namely, 1st. The Cepha- 
laspis Lyellii, of Agassiz, which appeared to be confined to Scotland, 
and perhaps the passage beds of Herefordshire, only represented in 
England by very well-marked varieties, 2nd. The common species 
of the Cornstones of England, which mighé be considered as identical 
with C. Lyell, but appeared to differ much in the form of the head. 
3rd. The Cephalaspis Murchisoni of Egerton, found in the passage 
beds near Ledbury. 4th. The Cephalaspis Salweyi, of Egerton, a 
species well characterised by its markings and the form of the 
head; and 5th. The Cephalaspis asterolepis, named by Dr. Harley, 
and distinguished by characters derived from the same parts as 
those of C. Salweyi. The C. ornatus of Egerton, Mr. Lankester 
stated, did not differ in its markings from the specimens of C. Lyelli 
lately obtained by Mr. Powrie, of Reswallie, and he therefore con- 
sidered it not impossible that these were specifically the same forms. 
There was not, the author remarked, sufficient evidence to justify 
the specific separation of C. ornatus. In C. Lyellii there existed so 
great a tendency to variation in the length of the cusps, breadth, &c., 
that it was extremely difficult to indicate specific characters with 
precision. Some very remarkable specimens of C. Lyellii, exhibit- 
ing the body and its ornamentation, were exhibited, being from the 
cabinet of Mr. Powrie. 
A Scotch species of Péeraspis, having the snout of Pé. rostratus 
and the dise of Pt. Crowehii, was then described. ‘The name re- 
tained for this species is that given by Mr. Powrie, Pt. Mitchelli, in 
honour of the Rev. Hugh Mitchell, of Montrose, who had been the 
first to recognise the existence of Pteraspis in the Scotch area of 
the Lower Old Red Sandstone. A monograph on the Old Red 
Fishes is in preparation for the Paleeontographical Society by Messrs. 
Powrie and Lankester, in which the various species of Cephalas- 
pidian fishes will be first dealt with. Assistance in the form of 
loans of specimens will be very acceptable to the authors. 
VI. On tHe Lower Lias or Lyme Rees. By E. C. H. Day, F.G.S. 
ee Lias was defined by the author as commencing imme- 
diately below the ‘Ostrea liassica’ series (with the Insect- 
beds, of Brodie); the érue ‘White Lias’ below, in his opinion be- 
longing, both upon physical and paleontological considerations, to the 
Rhetic group of rocks. 
The Lower Lias has been defined above by the upper limit of the 
zone of Ammonites varicostatus; and the author having accepted this 
definition in a former paper,* on the middle and upper divisions of 
this formation, he takes it as his boundary in the present description ; 
but he does so, with the belief that such a division is purely arbi- 
* Read before the Geological Society of London, 18th February, 1863. 
