R. Ballen Newton — Fossils from Sarawak, Borneo. 407 



Crafnaut, deserves a few words. It is girt iti by mountains on 

 either side, and to the south-west; the stream which drains the 

 lake flows in a north-easterly direction, through a gently sloping 

 valley filled with drift and alluvium. The narrowest part of the 

 valley is some distance above Pont Brwynog, about 100 feet below 

 the level of the lake. Here there are masses of rock in situ about 

 130 yards apart. The shape of the lake-basin is interesting ; the 

 deepest part is near the head of the lake, where it reaches 230 feet ; 

 for some distance the depth varies from 180 to 210 feet, and then 

 the lake shallows gradually up to the exit. If the lake is formed by 

 the blocking of this valley, the drift must be 130 feet thick at 

 the narrow area mentioned above, which necessitates a rate of fall of 

 two in three of the sides of the valley buried beneath the drift. 

 This is very much greater than the rate of fall on either side above 

 the drift. 



It is possible that in the case of Llyn Crafnant and Llyn 

 Geirionydd, one almost certainly a rock-basin, the other very 

 possibly so, earth-movements may have been wholly or partially 

 responsible for their formation. The same agency may conceivably 

 have operated in the case of Llyn Cawlyd. 



Llyn Eigiau lies to the east of Carnedd Llewelyn. It is quite 

 shallow, judging by the rushes which grow a long way into it. 

 The eastern shore is low and covered with peat, which probably 

 conceals moraine material. 



The writer is indebted to Mr. J. E. Marr, F.E.S., for many kind 

 suggestions and criticisms ; and to Mr. Kingsley for information as 

 to the depths of Llyns Geirionydd and Cawlyd. 



V. — On a Jurassic Lamellibranoh and some other associated 

 Fossils from the Sarawak River Limestones of Borneo ; 

 WITH a Sketch of the Mesozoic Fauna of that Island. 



By E. BuLLEN Newton, F.G.S. 



The Mesozgio Fauna of Borneo. 



CERTAIN deposits in the neighbourhood of the Seberuang River, 

 a tributary of the Kapuas in Western Borneo, were described 

 by R. Everwijn^ in 1854 as containing numerous so-called 

 " Nummulites." Similar organisms were obtained at a later date 

 from the same district by Dr. F. Schneider, which were examined 

 by Dr. K. Von Fritsch ^ and proved to belong to the genus Fatellina. 

 Two new forms were described and figured under the names of 

 P. scutum and F. trochus, whilst the occurrence of Patellina itself 

 suggested to Von Fritsch the probability of the beds in question 

 being of Cretaceous age. A further study of this material induced 



1 " Voorloopig onderzoek naar Kolem in de landschappen Salimbouw Djonkong en 

 Boenoet in de Residentie Westerafdeeling van Borneo " : Nat. Tijdsch. Nederlandsch. 

 Indie, 1854, vol. vii, p. 387. 



2 " Patellinem von der Westseite von Borneo" : Palseontographica, 1878, suppl. 3, 

 pp. 144, 145, pi. xix. 



