142 Geological Society: — 



on the Gulf of Xicoya. 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-dis- 

 trict 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 Eio Grande lignites are found. Below this is a 

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

 by the Bio Grande, on the Atlantic by the Bio Beventazon. 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 Woodwardian Museum 

 of the Universitv of Cambridge, probablv referable to OrnitTiopeif." 

 By Prof. H. G. Seeley, E.E.S., E.L.S., F.G.S., &c. 



3. " On the Xewer Pliocene Period in England." Bv S. V. "Wood, 

 Esq., F.G.S. (Concluding Part.) 



In this part the author continued, from the first part of the paper 

 (published in the Journal of the Society for 1880), his examination of 

 the conditions which accompanied the emergence of England during 

 the retreat of the ice of the Chalky Clay, and described the damming- 

 up of the valleys which drain to the "Wash by that ice after the 

 water-partings between their systems and those of the Severn and 

 Thames had emerged, whereby the fresh water hi these valleys was 

 raised, so as to overflow the minor water-partings within their sys- 

 tems and cover them with gravel, such as that at Casewick, within 

 the Welland system (described by Prof. Morris in vol. ix. of the 

 Journal), and those of Cambridgeshire, described by Mr. Jukes- 

 Browne. He referred the freshwater bed at Casewick, covered 

 by this gravel, and the palaeolithic brick-earth of Brandon and 

 Mildenball (which is overlain as well as underlain by the Chalky 

 Clay) to the time immediately antecedent to this — the slight advance 



