Geological Society of Loudon. 377 



Other examples are preserved in museums in Germany, and one in 

 Madrid, and most of them have been examined by the author, who 

 adduces the state of preservation of the small individuals, in contrast 

 with that of the traces of fish and Cephalopoda, the remains of food, 

 which are found in the stomachal region of the larger individuals, in 

 advance of the position occupied by the smaller ones, as a proof that 

 we have not here to do with a case of cannibalism. The position of 

 the smaller skeletons, with the head generally turned towards the 

 pelvic region of the larger ones, is also regarded as indicative of their 

 standing in the relation of parent and offspring. As some of the 

 young specimens possess limbs, it would seem that the supposition that 

 Ichthyosaurus passed through a sort of tadpole stage is erroneous. 



2. "On Rhamphocephalus Prestwiehi, Seeley, an Ornithosaurian 

 from the Stonesfield Slate of Kineton." By Prof. H. G. Seeley, F.E.S. 



In this paper the author described the characters presented by the 

 impression of the skull of an Ornithosaur in a slab of Stonesfield slate 

 from Kineton, near Stow-on-the-Wold, the peculiarities of which are 

 such as to induce him to found for it a new genus, to which he thinks 

 it probable that most, if not all, the known Stonesfield-slate Ptero- 

 dactyles may belong. It is distinguished especially by the great length 

 of the roof of the skull posterior to the orbits, by the presence of a 

 very deep constriction of the frontal region between the orbits, by the 

 strongly marked sutures between the bones, and by the curiously 

 Crocodilian character of the plan of structure of the roof of the skull, 

 which suggests the existence of a lower grade of Ornithosaurian 

 animals than has hitherto been suspected. The genus appears to be 

 allied to some forms of Rhamphorhynchus. The author names the 

 species, which is in the Oxford Museum, Rhamphocephalus Prestivichi, 

 and considers that the other bones of Ornithosauria discovered in 

 the Stonesfield slate support the generic separation of the group. 



3. "A Contribution to South-American Geology." By George 

 Attwood, Esq., F.G.S. 



The paper describes a line of country in Spanish Guayana, Vene- 

 zuela, S.A., commencing from a small town called " the Port of Las 

 Tablas," on the Orinoco River, extending about 150 miles, and con- 

 sisting of a series of crystalline and altered rocks. Syenite is the first 

 rock met with ; and then are found granite, quartz-diorite, haematite, 

 and magnetic iron-ores, gneiss, slaty rocks, gabbro, and diabase. 

 In the diabase the quartz-veins are found to contain large quantities 

 of gold mixed with the vein-matter; the alluvial soil in the neigh- 

 bourhood of the quartz-veins also contains gold nuggets and small 

 grains of gold. Although quartz-veins are found in great numbers 

 from the river to the interior, none of them have so far been found to 

 contain gold in any appreciable quantity until the diabase is met with. 

 All the rocks analyzed show a higher per-centage of silica than is 

 generally found in other localities. Three analyses made from one 

 piece of diabase showing two distinct lines of alteration by weathering 

 (on the original rock), prove that silica is readily dissolved under 

 atmospheric influences ; whilst alumina is not. Iron oxides contain 

 more oxygen near the surface than below it. Lime and magnesia are 

 both readily soluble ; but lime much more so than magnesia. Soda 



