S Professor Seeley. — Some Scientific [Sept. 16, 



arising straightest where the lava spread most continuously ; and this 

 is the history of the mode of formation of the rauge. Clearly 

 an amount of wear has been carried on by the action of rain, 

 &C, which has worn the softer clay, so as to leave the harder 

 layers of sandstone jagged and standing out in masses on the 

 slopes of the inclined plane. Well, as we went up this range, we 

 recognised different zones in the Karoo rocks, as we went from the 

 lower beds to the higher, and when I tell you that at the time of my 

 leaving England, no one there had the faintest conception of there 

 being any such divisions, no one knew whether any fossil which had 

 been sent to England came from the lower or the upper beds of the 

 Karoo, or whether it were possible to determine if there were lower or 

 upper beds, you will see we were on the track of investigations which 

 presented the possibilities of some great results, and we found as we 

 passed upwards that the kind of life changed. We left these 

 saurians, such as the pareiasaurians behind ; saurians which pre- 

 sented the semi-circular form of head, with the comparatively short 

 tail, though not quite so short as that of the lizard, but which do not 

 differ essentially from the type of the lower mammals at all, in 

 proportion as we see in the omithorhynchus, (which represents the 

 lowest type of mammals laying eggs and suckling its young) with 

 which we are acquainted. The upper beds of the rocks which we 

 examined now began to yield to us saurians of a somewhat different 

 nature ; the limbs were longer, the head somewhat different in form, and 

 furnished with marvellous tusks, whilst the body was somewhat more 

 arehed in its contour ; the hind limbs were better adapted for walking 

 on land, the tail apparently shorter than had been the case before, and 

 these animals possessed tusks which at first sight resembled the tusks 

 •of the dog tribe — the type which came to be known as the dicynodon 

 family, or the family of animals with the dog-like teeth. Now 

 these occurred in the zone of rock which goes immediately above 

 that which yields the large type of pareiasaurus. Going up higher 

 still, we lose these large animals, for many of them were large, some 

 with skulls almost rivalling the size of our largest terrestrial 

 mammalia, and which pointed to another group of animals altogether, 

 in which you will recognise a different type of teeth, as seen in the 

 example before you. Here you see dicynodons in which are a single 

 pair of tusks, lying at the side of the jaw, without any teeth in front or 

 behind, but here you will observe that there are the tusks still, and in 

 addition there are teeth, incisors, and teeth which correspond to our 

 grinders, or molars. These are at the back of the jaw. Well, these 

 shoAved the character of the rocks, and defined them, and the most 

 important discovery we made perhaps, or at all events one of the 

 most important, was that there is a succession of these types through 



