Geological Society. 517 



stone at Penbury (Penberry, Ord. Map) Hill, two and a half miles 

 north-north-east of St. David's ; at Llanllawer, two miles south-east 

 of Fishguard ; and at Carningley, one mile south of Newport. 



Though the summit of the principal Pembrokeshire chain is 

 roofing-slate, yet trap-rocks occur near the top, and are described by 

 the author as continuous through the district, extending to Plumb- 

 stone Mountain (five miles north-west of Haverfordwest) and to St. 

 David's Head, re-appearing at the Bishop and Clerks and the Hat 

 and Barrels rocks, and at the Smalls light-house. At Fishguard and 

 Strumble Head, three miles west of Fishguard Bay, the trap is co- 

 lumnar. On the north-east of the chain at Whitechurch (Eglwys- 

 wen), six miles south-east from Newport, on the east at Llanfirnach 

 (Llanfrynach, Ord. Map), and on the south at Llanglwydwen, are 

 beds of dark carbonaceous shale, which have been fruitlessly worked 

 for culm ; they appear to mantle round the trap, but preserve a 

 northerly dip ; they are accompanied by lead-veins, one of which, at 

 Llanfirnach, has been worked successfully. At Llanglwydwen Bridge 

 are indications of copper in a lode in contact with a considerable 

 bed of limestone. Mineral veins also exist along the coast, from 

 Newgate, in St. Bride's Bay, to St. David's Head. 



" Description of some remains of a gigantic Crocodilian Sau- 

 rian, probably marine, from the Lower Greensand at Hythe ; and of 

 Teeth from the same formation at Maidstone, referable to the genus 

 Polyptychodon," by Richard Owen, Esq., F.G.S. 



The fossil saurian remains from the lower greensand discovered 

 by Mr. H. B. Mackeson include portions of the iliac, ischial and 

 pubic bones, a large proportion of the shaft of a femur, parts of a 

 tibia and fibula, and several metatarsal bones. In consequence of 

 the absence of vertebrae and teeth, the determination of the specific 

 characters of this Saurian is, the author states, a subject of great 

 difficulty, and he therefore confines his remarks, in the present paper, 

 to indications of the characters by which it differs from previously 

 known extinct genera of Saurians. In the first place, Mr. Owen 

 shows, from the femur and other long bones having no medullary 

 cavities, but a central structure composed of coarse cancelli, that 

 the animal of which they formed part was of marine habits ; he, 

 however, adds, that the principal bone being a femur, independently 

 of the size and shape of the metatarsals, at once negatives the idea 

 that these remains belonged to the cetacean order ; and that the 

 form and proportions of the metatarsals equally forbid their reference 

 to any other mammalian genus. 



Femur. — The portions of this bone secured by Mr. Mackeson in- 

 clude about the two distal thirds, excepting the articular extremity. 

 Its length is two feet four inches, its circumference in the middle or 

 smallest part of the shaft is fifteen inches six lines, and at the broken 

 distal end, two feet five inches. These dimensions prove that the 

 animal was equal to the most gigantic described Iguanodon*. If 



* Femur of the Iguanodon, — length, 4 feet 6 inches ; smallest circum- 

 ference, 1 foot 10 inches. 



