STRATIGRAPHIC PALEONTOLOGY. 97 



is of old Miocene age. The coral fauna comprises about 19 species, only 

 about four of which, Placocyathus n. sp. b, Stylophora n. sp. with a com- 

 mensal worm, Thysanus corbicula Duncan, and Pontes n. sp. with a com- 

 mensal worm, seem to be confined to the formation; most if not all the 

 other species range upward into the Gurabo formation, and at least two 

 species, Solenastrea bournoni M. Edw. and H. and Siderastrea siderea 

 (Ell. and Sol.), have persisted until Recent time. The most abundant or- 

 ganisms are Mollusca, of which about 500 species have been recognized. 

 The characteristic species are Conus cercadensis Maury, Cancellaria 

 (Aphera) islacolonis Maury, Area (Scapharca) corcupidonis Maury, Area 

 (Scapharca) arthurpennelli Maury, Pecten (Aequipecten) n. sp. a, Cardium 

 (T r achy car dium) dominicanum Dall, and Corbula (Bothrocorbula) viminea 

 Guppy. The largest faunule, 260 species, was collected on Rio Mao at 

 station 8525, which is Doctor Maury's "bluff 3." 1 The faunule on Rio 

 Albano (station 8729) is remarkably like the faunule at station 8525, 

 though the two localities are far apart geographically. The Cercado 

 faunule on Rio Cana (station 8534) is characterized by the substitution of 

 peculiar specific stocks for many species that are conspicuous at other 

 localities of the Cercado formation. 



Because of the apparent specific identity of several species of corals in 

 this formation with species found in the Bowden marl of Jamaica Vaughan 

 correlated it with the Bowden marl, but there is considerable similarity 

 between the corals of the Gurabo formation and those of the Bowden, and 

 this is true of other organisms, so that the Cercado formation is probably 

 a little older than the Bowden. (For fuller discussion see pp. 98-99.) 



Modified Cercado Fauna. 



Cercado faunules that are modified by the first appearance of a number 

 of species of mollusks that elsewhere are confined to the overlying Gurabo 

 formation were collected on Rio Mao (station 8522) and on Rio Gurabo 

 (station 8739). These species are Terebra sulcifera Sowerby, Conus 

 haytensis Sowerby, Conus multiliratus Bose subsp. gaza Brown and Pilsbry, 

 "Clavatula" labiata Gabb, Cancellaria guppyi Gabb, Lyria pulchella (Sow- 

 erby), 2 Metulella venusta (Sowerby), Distortio simillima (Sowerby), Pecten 

 {Aequipecten) eugrammatus Dall and Echinochama antiquata Maury not 

 Dall. All these species are abundant at one or more localities of the Gurabo 

 formation and, moreover, the above list includes six superspecific groups 

 that are not known in the typical Cercado fauna. 



According to Doctor Maury's faunal lists her expedition collected a simi- 

 larly modified Cercado faunule from "Zone G," Rio Gurabo. 3 The 

 faunule of "Zone G" includes four species that are found in the Gurabo 



1 Maury, C. J., Bull. Am. Paleontology, vol. 5, p. 425, 1917. 



2 This species is reported by Maury from the Cercado formation at "Bluff 3," Rio Mao ( = station 8525). 



3 Maury, C. J., Bull. Am. Paleontology, vol. 5, pp. 439-440, 1917. 



