4 Dr. L. Adams on the Geology of the Maltese Man ds. 



from this bed into the Marl is not so gi-adual as in the other 

 deposits, forming often an abrupt line of demarcation between 

 the reddish-yellow freestone and the loose clay. The latter bed 

 varies in thickness : in the island of Gozo it is well developed, 

 where often a thickness of from 40 to 50 feet is discernible ; in 

 other situations it thins out to a few feet. The fossil remains 

 of the Marl are apparently not so numerous or so well preserved 

 as in the other formations. Casts of shells are common, and 

 often incrusted with iron, which, in the same form as just de- 

 scribed, strews the bed in great abundance, together with quan- 

 tities of lamellar gypsum. The Marl is a grey or drab-coloured 

 clay, more or less tenacious, with lighter-coloured bands running 

 horizontally throughout the bed. Passing upwards, we find a 

 gradual passage into the Sand-htdi, which is composed of a black 

 or green-grained glistening sand, intermixed with grey-coloured 

 calcareous particles or a reddish sand; the latter is at once cha- 

 racterized by the enormous numbers of the little foraminiferous 

 shell Heterosiegina depressa, which is met with in great abund- 

 ance throughout this bed and the lower part of the one above it. 

 The thickness of the Sand-bed, like the last, is very variable. 

 In Gozo cliflP, sections of 50 feet in thickness are not uncom- 

 mon; but on the south-west coast of Malta it seems to thin out 

 to a few feet. The fossils of the Sand-bed are both numerous 

 and very well preserved. Teeth, bones, &c., of Delphinus are 

 common. The Squali are well represented. Among the Mol- 

 lusca, beds of Ostrea Virleti and 0. Deshagesii are common; 

 also beds of Terebratula ampulla, var. sinuosa, Brocchi, and 

 Megerlia truncata. Among the Echinodermata, Clypeaster altus 

 and C. marginatus are very common. 



The passage from the Sand-bed to the Upper Limestone is 

 usually gradual; sometimes it merges into a red- and black- 

 grained Sandstone (i. e. Heterostegina-hed), then into a red or 

 white limestone abounding in Corallines and characterized more 

 or less by the quantities of Rhynchonella bipartita, Terebratula 

 ampulla, var. sinuosa, and Argiope decollata. The last-named 

 variety usually passes into a white calcareous sandstone, either 

 compact or soft and porous, but always abounding in casts of 

 Pecten, Trochus, Area, Haliotis. The upper portion of this bed 

 is usually an open-grained coarse rock, containing fissures and 

 cavities lined with calcareous incrustations. The absence of the 

 Squali from the middle and upper parts of the Upper Limestone 

 we have repeatedly remarked; whereas such Echinoderms as 

 Bnssus lotus, Brissopsis Duciei, and Clypeaster Redii have been 

 hitherto only met with in this bed. 



The thickness of the Upper Limestone varies; its average is 

 calculated at 100 feet; but some portions far exceed that mea- 



