538 P. W. Stuart- Menteath — The Age of Pyrenean Granite. 



mm. 



Length of upper p. 1 9 



Transverse width of p. 1 6 '5 



Length of p. 2 6*5 



„ P-3 5 



p. 4 ... ... 2-5 



Antero -posterior dimensions of C. at base 4 



Dimensions of mandibular ramus : — mm. 



From anterior border of canine to posterior border of m. 2 ... 44- § 

 ,, ,, ,, of condyle 61 



Lengthofm. 1 11-5 



p. 1 7 



„ p. 2 6 



„ P- 3 5 



Trochictis pusilla, sp. nov. 

 A diminutive species of Trochictis is represented by a fragmentary 

 left mandibular ramus with m. 1 and p. 1 in place and the alveolus 

 of m. 2. M. 1 exhibits the characteristic very elongate talon of 

 the genus, with a delicate crenulation of the internal upper margin 

 of the talon, as in T. taxodon. 



m. 1 = 6 mm. 

 p. 1=3 ,, 

 Height of mandibular ramus below m. 1 (int.), 3*5 mm. 



IV. — The Age of Pyrenean Granite. 

 By P. W. Stuart-Menteath, Assoc. R. S. Mines. 



AN easy walk from Lourdes through Lesignan, Pareac, Orincles, 

 Leyrisse, and Benac, to the return station of Ossun, traverses 

 the entire outcrop of the Upper Cretaceous Flysch, lying between 

 the abrupt uprise of the Cenomanien limestone at Lourdes and the 

 Danien that skirts the Tertiary plain towards Tarbes. The age of 

 this Flysch is admitted ; every objection regarding it has been 

 successively abandoned ; and its appearance, composition, and 

 characteristic fucoids are as typical at Lourdes as at any point 

 within fifty miles on either side. By insensible gradations it passes 

 repeatedly from fresh marly shale with characteristic fucoids into 

 micaceous schists that have been classed as Cambrian. Portions of 

 a sandy character acquire vivid colouring and pass insensibly into 

 a rock indistinguishable from decomposed granulite, while preserving 

 their original bedding. Such changes occur on either side, or on 

 the prolongation, of extensive lenticular intrusions of solid granite, 

 which cross the indicated route between Pareac and Orincles and 

 between Orincles, Visker, and Benac. Across both altered and 

 unaltered Flysch, large and small dykes of crushed schist, filled 

 with angular blocks of granite, quartzite, etc., vertically intrude, and 

 increase in number and size as the granite is approached. When 

 these dykes appear they are accompanied by thin veins of granite 

 cutting across the Flysch. These veins gradually increase in 

 number, and insensibly blend into the solid granite already 

 mentioned. At Leyrisse the passage is admirably exposed in fresh 

 road-cuttings, both on approaching the granite from Orincles and on 

 leaving it towards Benac. The hypothetical assumption of islands 

 of old rock in the Flysch has been proposed and subsequently 



