154 Geological Society. 



in the main presented the character of a young existing Crocodile 

 coupled with distinctive features. The centrum of the cervical ver- 

 tebra is oblique, and the neural canal of the dorsal vertebra is small 

 as in Hyposaurus. The species is of small size. 



15. " On the base of a large Lacertian Skull from the Potton 

 Sands." By Harry Govier Seeley, Esq., F.L.S., F.G.S. 



This specimen was interpreted by the author as the anchylosed 

 basioccipital and basisphenoid of a Dinosaur. It showed a resem- 

 blance to Crocodiles in its posterior aspect, but in all other respects 

 was Lacertian ; it makes a close approximation to Hatteria, and in 

 no respect shows affinity to birds. The pterygoid processes look 

 downward, and the basioccipital condyle looks downward and 

 backward. The base of the brain- cavity is long and narrow, while 

 its anterior border corresponds to an imperfectly ossified fibrocarti- 

 lage seen in the same position in Hatteria. The author did not 

 regard the specimen as giving support to Prof. Huxley's hypothesis 

 of the Avian affinities of Dinosaurs. 



16. " A Section through the Devonian strata of West Somerset." 

 By Harry Govier Seeley, Esq., F.L.S., F.G.S. 



In 1867 the author had visited the Devonian country in search 

 of the fault which Mr. Jukes supposed to traverse Devon and West 

 Somerset. He satisfied himself by sectional evidence that no fault 

 existed, and in a section from Hurlstone Point to Brushford has 

 noted down the mineral character of the successive groups of strata 

 forming the country, and the only folds of the strata seen by him on 

 that line of section. He thought that Mr. Etheridge's detailed 

 grouping of the rocks was better suited to the N.W. part of the 

 country than to West Somerset, and that for that region the divisions 

 of strata used by Mr. Jukes were convenient. 



17. " On the Pectoral Arch and Pore Limb of OpTithalwiosaurus." 

 By Harry Govier Seeley, Esq., E.L.S., F.G.S. 



After some remarks on the structure of the pectoral arch in Ich- 

 thyosaurus, the author described parts of a skeleton discovered by 

 Mr. Leeds in the Oxford Clay, on which he founded the genus 

 Ophthalmosaurus. 



The pectoral arch comprised the usual bones ; but their relation to 

 each other was unusual. The clavicles form a strong arch; the 

 lateral clavicles join behind by interlacing sutural union, and not 

 by overlap ; while in front the episternum (or interclavicle) is 

 wedged in between them so as to divide them. The coracoids are 

 expanded and grasped by the clavicles in a depression in their mar- 

 gins ; the scapula is large. 



The humerus shows the usual Ichthyosaurian characters, and has 

 three facets at the distal end. To these correspond three bones in 

 the forearm, the olecranon-ossification being two thirds as large as 

 the radius. The single row of carpal bones includes four elements. 



