Geological Society of London. 287 



5. The palatal area is very narrow in front and wide behind, with steongly curved 



lateral boundaries. 



6. The posterior maxillary and palatal teeth are multiserial. 



7. The rami of the mandible are united in a long symphysis, behind which they 



diverge widely, and the dentigerous edges are strongly concave upwards as 

 ■well as outwards. 



8. The mandibular teeth in front are set into a close, apparently continuous 



palisade, and become distinct and conical only at the posterior end of the 

 series. 



9. The fore foot is remarkably short and stout, with metacarpals of equal length. 



The relations of Khijncliosaurus to Hyperodapedon and Sphenodon 

 were then dealt with, the first-named being shown to occupy in 

 some respects an intermediate place between the two others. The 

 skull of Bhyncliosaurus resembles that of Hyperodapedon in its single 

 anterior nasal aperture, its premaxillary and mandibular rostral 

 processes, and in having more than one series of palatal teeth ; 

 but in general form and in the shape of the maxillee, palatal bones, 

 and rami of the mandible, it departs far less from Sphenodon than 

 Hyperodapedon does. Some comparisons of limb-bones were also made. 



The three genera mentioned were shown to form a particular 

 group, which, however, had no claim to ordinal distinction, and 

 appeared to form a family, Sphenodontid^e, of the Lacertilia, com- 

 prising two subfamilies, RhynchosaurinEe (including Bhynchosaurus 

 and Hyperodapedon) and Sphenodontinje. 



The fact that in this Lacertilian group the highest known degree 

 of specialization, as shown in Hyperodapedon, was attained as early 

 as the Triassic epoch, showed that in Permian times, or earlier, 

 Lacertilia existed which differed less from Sphenodon than either of 

 the Rhynchosaurinse did. Not only was the Lacertilian type of 

 organization clearly defined in the Triassic epoch, but it attained a 

 degree of specialization equal to that exhibited by any modern lizard. 



2. " Eocks of the Essex Drift." By Rev. A. W. Rowe, M. A., F.G.S. 



The rocks of the Essex drift are of great variety. There is a 

 remarkable absence of granite of any kind, and only two specimens 

 of syenite have been found. Quartz-porphyrites and quartz-tourma- 

 line rocks are fairly abundant, felsites are rarely met with, but felspar 

 porphyrites are very abundant ; trachytes also are found, but there is 

 some reason for suspecting that these do not really belong to the drift, 

 but have been imported in very early times. Tlae most abundant of 

 the igneous rocks are the dolerites ; but all the coarser dolerites 

 and those of a true ophitic character are wanting. Many of the 

 specimens are of subophitic texture, and bear a general likeness to 

 the subophitic dolerites of Central England. Some specimens, how- 

 ever, are strikingly like the rocks of the Whin Sill, in certain special 

 points. The dolerites of trachytic texture, or basalts, do not at all 

 resemble those of the North of England, but some of them are almost 

 identical with certain Scandinavian basalts. One or two specimens 

 deserve special mention, and among them a hypersthene-bearing 

 dolerite that is more nearly ophitic than any of the others. Two 

 specimens of granulite containing hypersthene are interesting as 

 belonging to a well-characterized type. The crystalline schists are 



