590 PROF. J. W. GREGORY ON [Nov. I9II, 



(/) Merj to Ptolemeta. 



To determine the succession, of the rocks in this part of Cyrenaica, 

 a traverse was made from the plateau-scarp south of Merj to the 

 coast, near its ancient port, Ptolemais or Ptolemeta. 



The relations of the rocks between the plain of Merj and the 

 Wadi Hamema, through which we descended to the shore, are 

 uncertain, as, owing to a misadventure, I had to return to Merj 

 by a night journey. The general section from the plateau south 

 of Merj to the sea at Ptolemeta is illustrated by fig. 3 in PI. XLII. 

 The coastal plain near Ptolemeta consists of dunes along the shore, 

 of large delta-fans before the mouths of the wadis, and of wide 

 sheets of alluvium in the intervening depressions. The delta-fan, by 

 which the track from Merj to Ptolemeta reaches the coastal plain, 

 rises to the height of 340 feet. The rocks above it are chert- 

 bearing limestones and marls, belonging to the Apollonia Limestone 

 Series, which continue up to the level of over 940 feet. The rocks 

 are dipping northwards, in places as much as 25°, the steep dip 

 being doubtless due to the proximity of the Tokra Fault, although 

 there may be parallel faults which I did not detect. 



The rocks crossed during the ascent on to the plateau from the 

 shore (see PI. XLII, fig. 3) begin above the delta-fan, at the level 

 of 340 feet, with a dark-grey, compact, dolomitic and siliceous lime- 

 stone. The rock is succeeded above by a chalky granular limestone 

 with some black grains, which microscopic examination shows to be 

 glauconite. This rock, at the height of about 440 feet, includes an 

 oolitic band, in which Mr. D. P. Macdonald has recognized well- 

 preserved echinoid spines, nullipores, and foraminifera. A similar 

 rock occurs in the chalky limestone at Wadi Nagr, west of Derna. 



This rock is succeeded by a compact, unfossiliferous, chalky lime- 

 stone with a rough granular surface. Mr. Macdonald describes it 

 as containing some calcite crystals and occasional grains of quartz. 

 Then follows, at the level of from 500 to 550 feet, a series 

 of compact chalky limestones with some grains of glauconite. Mr. 

 Macdonald found in the chalky base some Globigerinae, sponge- 

 spicules, and a holothurian plate. The rock includes some layers 

 of marl and nodules of chert. 



At the level of 620 feet the track crosses a small col into the 

 Wadi Hamema, which has beheaded the gully followed by the 

 route to Ptolemeta. At this level and up to over 650 feet, the 

 rock is a siliceous limestone with abundant chert-nodules. The 

 matrix of this rock, according to Mr. Macdonald, consists of a close 

 calcareous paste with some grains of quartz and glauconite, and 

 it also contains Globigerina and a holothurian plate. The chert- 

 bearing rocks are exposed up to the height of 950 feet. 



The northern part of this series of beds consists of chalky lime- 

 stones like those of the Wadi Nagr, and they belong to the upper 

 portion of the Apollonia Limestone Series. The limestones from 

 the level of 500 to 600 feet containing the large chert-nodules 

 represent the lower part of the same series. 



