Dr. R, Broom — A neio Stegocephalian Reptile. 499 



of abates is taken practical advantage of by German manufacturers 

 in the preparation of agates for the market, beautiful internal 

 dendritic markings, which add so much to their market value, 

 being produced by soaking the agates in a succession of liquids. 

 In ray Belfast address, however, I did not consider the case of the 

 permeability of cold crystals by cold solutions. On the csntrary, 

 my main object was to impress upon my hearers the fact " that 

 heat increased the porosity of minerals, facilitated the passage of 

 liquids laden with mineral matter through their pores, and increased 

 the potency of chemical action." 



In the course of my remarks I referred to numerous instances 

 in which there was good evidence to show that crystals and rocks 

 had been permeated by chemical reagents, and I need not go into 

 these cases again. I do not see how the schillerisation of minerals 

 or the formation of a pseudomorph of one mineral in the form of 

 another can be accounted for if you do not believe in the permeability 

 of heated rocks and crystals by heated chemical reagents. I foresaw 

 that the idea of cracks and their subsequent obliteration would 

 suggest itself to some minds, and in my Belfast address I said all 

 that I considered necessary in reply to this suggestion. 



V. — On a new STEaooEPHALiAN {Bateachosuohvs Browni) from 

 THE Karroo Beds op Ariwal North, South Africa. 



ByE. Broom, M.D., B.Sc, C.M.Z.S. 



IN the collection of Mr. Alfred Brown, of Ariwal North, there 

 is a fairly complete skull of a moderate-sized Stegocephalian 

 which differs very considerably from that of any form hitherto 

 described. The specimen is in a sandstone matrix. Owing to 

 a crack produced by weathering practically all the cranial bones 

 adhered to the counter slab when an endeavour was made to 

 display the remains. The sculpturing of the bones is thus hidden, 

 but the sutures are for the most part distinctly seen. Fig. 1 

 represents a slightly restored view of the upper side of the skull. 

 The most striking features are the great breadth of the skull and 

 the relatively advanced position of the orbits. In these respects it 

 makes a slight approach to the condition found in the American genus 

 Diplocaulus. There is no distinct notch in the post-temporal region, 

 as in most Stegocephalians, and there are no ' epiotic ' cornua. 

 There are two rudimentary cornua on the posterior cranial border, 

 but they are formed by the so-called ' supra-occipital ' bones. In 

 the middle line between the frontals and nasals is a median bone, 

 probably an ethmoid. I fail to detect a supra-temporal element 

 as distinct from the quadrato-jugal, which is of large size. 



The under surface of the skull has only been partly cleared of 

 matrix. The occipital region is well ossified and extends far 

 backwards. The condyles are well developed. The most note- 

 worthy feature of the palatal surface is the large size of the 

 pterygoids. These, with the ' parasphenoid,' form more than a third 

 of the under surface of the skull. The pterygoids also form two 

 large descending plates, which lie close to the inner sides of the 



