ON SUBFOSSIL PRIMATES PEOM MADAGASCAR. 63 



Ankaratra Mountains. Volcanic cones are thickly scattered over a large part of this 

 district, and at many points extensive lava-streams of varying age are plainly visible. 



The fossiliferous marsh occurs in the course of the River Mazy, an affluent of the 

 Sakay, the waters of which discharge themselves into the Mozambique Channel. The 

 Mazy, after traversing a region of primitive rock in a westerly direction, encounters 

 several streams of lava which have entirely deflected it from its ancient course. 

 There is evidence of the recent drying up of extensive lakes in the neighbourhood, 

 of which fact the traditions of the natives give confirmation. 



A reference to the accompanying contour map (text-fig. 2) showing the results of a 

 careful survey of the region by M. Berthier, Administrator of the District, and which 

 by the courtesy of the late M. Jully I am able here to reproduce, will show that above 

 the fossiliferous marsh the Mazy has cut its course for several kilometres through an 

 ancient lava-flow and that on encountering the primitive rock it has followed the line 

 of division between this formation and the volcanic output. 



The fossiliferous marsh itself is roughly semicircular in form. It is bounded on its 

 semicircular contour by the River Mazy, the bed of which now lies some five metres 

 below the surface of the marsh. On its other sides it is limited by a stream of lava, 

 the surface of which shows it to be of much more recent date than that traversed 

 by the river in its higher reaches (text-fig. 3). 



A calcareous deposit several metres thick and of great hardness separates the marsh 

 from the river, and it is no doubt to the presence of this broad bank of limestone that 

 the preservation of the fossiliferous deposits is due. 



The marsh when trenched presents considerable variety in the sections exposed. 

 Over large areas there are deposits of travertin in varying thickness. This in many 

 parts forms an unbroken sheet which greatly impedes the work of exploration ; here 

 and there this sheet is replaced by detached nodules, and over considerable areas the 

 lime-deposits are absent. Mineral springs are abundant, but all are now cold. They 

 are of varying mineral constituents, some being strongly impregnated with iron and 

 many highly charged with carbonic acid. From these springs the deposit of lime is 

 still forming. 



On making a section through a part of the marsh where the layers of limestone are 

 discontinuous, various strata are successively encountered. 



To a depth of about 1 metre below the present surface the deposits consist of recent 

 vegetable remains succeeded by a fine black humus which rapidly turns to mud on 

 admixture with water. This is superposed on a stratum of forest debris, consisting of 

 leaves, twigs, seeds, and fruits of numerous species. Below this again a layer of larger 

 blanches and tree-trunks is frequently encountered. These vegetable remains are in a 

 wonderful state of preservation, the leaves often retaining their green colour. The 

 bones begin to appear in general with this layer of wood, though they are occasionally 

 met with nearer the surface. 



