82 J. W. SPENCEit — GEOGRAPHICAL EVOLUTION OF CUBA. 



In the region of Matanzas the t3qjical heds lie unconformably upon 

 the Miocene. Thus, on the northern side of the Yumuri gorge, between 

 the church and the first lateral ravine, there are about 150 feet of this 

 earthy limestone in beds dipping about 15° north 10° east. It also rises 

 and caps the ridge upon the western side of Matanzas bay, and consti- 

 tutes much of the case-hardened roadway on the ridge. At the sunamit 

 of the ridge, crossed by the road from Matansas to Corral Nuevo, the 

 lower part of the Matanzas series is composed of fine, soft, calcareous, 

 mealy powder, with little or no siliceous matter, but it contains water- 

 worn pebbles of the older Tertiar}^ limestones. These materials rest un- 

 conformably upon the eroded surfaces of the older Tertiary limestones. 

 This series the writer has denominated Matanzas formation, a^ a distinctive 

 name is necessary. The appellation of " white limestone " has been 

 given to the same formation in the other parts of the West Indies, but 

 it is also used for both Eocene and Miocene deposits. Again, the forma- 

 tion has been confused with coral reefs and other coastal limestones. 

 The section at Matanzas lies unconformably upon fossiliferous Miocene 

 beds and unconformably beneath the modern raised coral reefs of the 

 coast. Much of both the cities of Matanzas and Havana rest upon this 

 Matanzas formation, and the material is used for building })urposes. 



The Matanzas formation partly filled the Yumuri valley after the 

 erosion following the deposition of the Miocene limestones. Beneath 

 the Montserrat church and resting unconformably upon Eocene strata 

 (for the Miocene had been removed in the excavation of the valley) the 

 marls were found to contain a considerable number of fossils. The spe- 

 cies of those determined are modern in types. A few small corals were 

 not determined. The shells were kindly identified by Mr Charles T. 

 Simpson, of the Smithsonian Institution. The marine shells are — 



Strombus puyilis, Lin. Area holmesi, K. and St. 



Massa vibex (?), Say. Area americana, Gray. 



Tectarius muricatus, Lin. Perma ephippus (?), Lin. 



Lucina tigrlna, L. Venus cancellatus, Lin. 



Lucina jamaicemis, Lam'k. Ostrea virginica, Gm. 



A few land shells were also present, some of which had been washed 

 into the sea, in which the other shells were living. They belong to the 

 following species : 



Pleurodonta auricoma, Fer. Chondropoma pfeifferianum, Poey. 



Helix bonplandi, Lam'k. Chondropoma dentatum, Sa}'. 



Liquus fasclaius, MuL Ctenopoma rugulosiis, Pf. 



Cyllndrella lavalleana, Orb. Magalomastoma bicolor, G'l'd. 



Macroceramus turricula, Pf. Ilelicina submarginata (?), Poey. 



Strophia incrnsata, Reeve. Helicina zephyrina, Duel. 



