--------------------------+-------------+--------------+------------- Composition. |Tripoli from | Tripoli from | Tripoli from | Licata | Grotte | Caltanisetta | (Fremy). | (Schwager). | (Mottura). --------------------------+-------------+--------------+------------- Silica, | 30.98 | 58.58 | 68.6 Alumina, | 17.54 | 11.51 | } Oxide of iron, | 0.33 | 1.84 | } 3.6 | | | Lime, } | 38.09 | { 8.49 | } Magnesia, } | | { 0.41 | } 12.1 | | | Water and organic matter,}| | { 11.26 | } Carbonic acid, }| 13.06 | { 7.12 | } 15.2 +-------------+--------------+------------ | 100.00 | 99.21 | 99.5 --------------------------+-------------+--------------+------------- B. The Radiolarian marl of the Mediterranean appears, judging by the accounts already published, to stretch along a considerable part of the coast in the earlier and middle Tertiary formations; thus it occurs of similar composition in widely separated localities, in Sicily, Calabria, Zante, and Greece; in North Africa from Tripoli to Oran and probably much farther. So long ago as 1854 Ehrenberg, in his Mikrogeologie (L. N. 6) gave a series of important, even if incomplete, communications regarding the "chalky white calcareous marl of Caltanisetta" (Taf. xxii.), the "Platten marl of Zante" (Taf. xx.), the "plastic clay of Ægina" (Taf xix.), and the "polishing slate of Oran" (Taf. xxi.). In 1880 Stöhr showed in his fundamental description of the Tripoli from {clxxii}Grotte in Sicily (L. N. 35) that its Radiolarian fauna is much richer than Ehrenberg supposed. The same is the case in the Tripoli of Caltanisetta, and also in the Baden marl of the Vienna basin. The richest deposit appears to be the pure Kieselguhr-like Tripoli from Oran; a small specimen, which was recently sent to me by Professor Steinmann of Freiburg, i. B., contained many hitherto undescribed species, and was at least as rich as the purest Barbados marl.