330 Reports and Proceedings — 



IL— May 24, 1882.— 1. ''On the Geology of Costa Eica." By 

 George Attwood, Esq., F.G.S., F.C.S., Assoc. Memb. Inst. C.E. ; with 

 an Appendix by W. H. Hudleston, Esq., M.A., F.G-S., F.C.S. 



The author commenced his journey at the town of Punta Arenas, 

 on the Gulf of Nicoya. This stands on a peninsula composed of a 

 calcareous sandstone, covered by a dark sand consisting of quartz 

 grains, magnetite, and decomposed felspar and augite. Inland is an 

 igneous rock which occupies, before long, both banks of the Eio 

 Barranca, and on the left bank extends to the sea ; it is a greenstone 

 containing porphyritic crystals of augite and triclinic felspar, and 

 appears to contain too much silica for a true dolerite, being rather a 

 representative of one of the more basic forms of the augite-andesites, 

 resembling, in some respects, specimens from the English lake- 

 districts described by the late Mr. Clifton Ward. On this rock, after 

 a time, are found boulders of a black augite-andesite ; this appears 

 to be identical with the rock found in situ in the Aguacate moun- 

 tains. Here are gold- and silver-mines, which were described. In 

 the ravine of the Rio Grande lignites are found. Below this is a 

 series of ancient lakes, which on the Pacific slopes have been tapped 

 by the Eio Grande, on the Atlantic by the Rio Eeventazon. Here 

 also the country rock is the greenstone already described ; and near 

 Cartago there are boulders of trachyte. The volcano of Irazu is a 

 trachyte, probably a quartz-trachyte, forming an important building- 

 stone. Augite-andesites are found at La Palma, about twelve miles 

 N.W. of the volcano. Irazu, a volcano at present passive, but with 

 blow-holes of gas, is between 11,000 and 12,000 feet in height. 

 Turrialba, of about the same elevation, is still feebly active. 



The author is of opinion that the filling of the mineral lodes 

 (ancient fissures) in the Aguacate mountains took place in Tertiary 

 times, probably Pliocene, and that this infiltration was contempo- 

 raneous with the eruption of the augite-andesites in the same region. 

 The quartz-trachytes and sandstones are certainly Post-Tertiary. 



2. " On a remarkable Dinosaurian Coracoid from the Wealden of 

 Brook, in the Isle of Wight, preserved in the W^oodwardian Museum 

 of the University of Cambridge, probably referable to Ornithopsis." 

 By Prof. H. G. Seeley, F.R.S., F.L.S., F.G.S., etc. 



The specimen described was obtained in 1866 by Mr. Henry 

 Keeping, midway between the fossil forest at Brook Point and Brook 

 Chine, about 10 feet above high-water mark. The author stated 

 that it was the largest Dinosaurian coracoid known to him, that it 

 differed in important characters from that of Iguanodon, and that, of 

 described genera, it most probably belonged to OrnitJiopsis. The 

 bone is from the right side, and nearly perfect ; its length is about 

 ] 6^ inches and its greatest breadth about 14 inches ; the humeral 

 articular surface is nearly 8 inches, and the suture for the scapula 

 about 10^ inches long. The bone is moderately thick, slightly con- 

 vex externally and concave within, thickened at the humeral articu- 

 lation. The nearest approach to this coracoid is made by that of 

 the skeleton referred to Hylceosaiirus, from the Wealden of Tilgate ; 

 but in it the distal portion of the bone is more prolonged, the median 



