MUSEUM OF COMPARATIVE ZOOLOGY. 251 



merits of marine lime mixed with the calcareous debris of the life of the 

 ocean's margin, with, in places, an almost imperceptible proportion of 

 the finer physical sediments of the nucleal island. 



While these limestones and alternating beds have a great areal extent, 

 it would be a mistake to assign to them a proportional thickness, for 

 accurate measurements will not make their thickness anywhere greater 

 than one thousand feet. 1 estimated from the dips in the Rio Armen- 

 daris section tliat tliey were from eight hundred to one thousand feet ; 

 the incomplete section in the canon of the Yumuri of Matanzas reveals 

 eight hundred feet ; the canon of the Yumuri of Baracoa shows six hun- 

 dred feet ; the summit of Ynnque displays less than one thousand feet ; 

 while the section from fourteen kilometers south of Havana to Bata- 

 bano is not over one tliousand feet. (Plate 11. Fig. 1.) In fact, they 

 may be said to constitute a comparatively thin veneering over the old 

 metaraorpliic tioor. 



The old limestone formations occur from end to end of the island, and 

 extend in many places completely across it down to water level. Their 

 continuity is interrupted only by erosion along the central axial region, 

 and only the low portion adjacent to sea level is covered by later deposits. 

 De Castro's geologic map of Cuba ^ shows in an excellent manner their 

 general disposition. In places, as between Mata and Yumm-i, they form 

 the north wall of the coast. They cap the highest eminences of the 

 island seen by me, overlooking all other rocks, being overreached only 

 b}' the Sierra Maestro, the geology of which is unknown. Their close 

 proximit}' to the north coast and their abrupt protubei'ance above the 

 newer formations have an important bearing on the history of the island 

 as a whole. So extensive is this old limestone formation, and so abruptly 

 does it rise above the coast, that, if all the coastal formations were 

 stripped away, or if the island should subside for one hundred feet, its 

 superficial extent would hardly be perceptibly diminished or its outline 

 materially altered. 



The greater part of these limestones seen by me are of Eocene and 

 Miocene or of Pliocene age, as alleged by De Castro. In the Armendaris 

 section, near Havana, they arc both Eocene and Miocene, as has been 

 asserted by De Castro and others, and as is shown by my collections.^ 



1 Croquis Geologica de la Isia de Cuba, por D. Manuel Fernandez de Castro, 

 ampliado por T>. Pedro Sallerain y Legarra. 18G9-8o. Printed in Vol. IX. of the 

 Congreso Internacional de Aniericanistas. 



- The determinations of age in tliis paper are hased upon the palcontologic 

 determinations of l^r. William H. Dall, of the U. S. Geological Survey, who kindly 

 examined the material collecicd. 



