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52 CONTRIBUTION TO THE PALEONTOLOGY OF TRINIDAD. 



Venericardia planicosta Sowerby, Min. Conch., 1, pi. L, 1814. 



Venericardia planicosta, Deshayes, Coq. Fos. des Envir. de Paris, 1, p. 142, pi. 24, figs. 1-3, 1824. 



Venericardia planicosta Conrad, Jour. Acad. Nat. Sci. Phila., vol. VI, pp. 213, 214, 215, 1830. 



Cardita planicosta Deshayes, Enc. M6th. Vers., II, p. 198, 1830. 



Venericardia ascia W. B. & H. D. Rogers, Trans. Am. Phil. Soc, 2d ser., vol. V, p. 374, pi. 29, 



fig. 2, 1839. 

 Cardita densata Conrad, Jour. Acad. Nat. Sci. Phila., 2d ser., vol. I, p. 130, pi. 14, fig. 24, 1848. 

 Cardita planicosta Conrad, U. S. Mexican Boundary Surv., p. 161, pi. 19, figs. 2, a, b, 1857. 

 Cardita hornii Gabb, Geol. Surv. Cal. Paleont., vol. I, p. 174, pi. 24, fig. 157, 1864. 

 Venericardia planicosta var. regia Conrad, Am, Jour. Conch., vol. I, p. 8, 1865. 

 Venericardia mooreana Conrad, Am. Jour. Conch., vol. Ill, p. 190, 1867. 

 Venericardia planicosta Conrad (Heilp.), Proc. Acad. Nat. Sci. Phila., p. 366, 1880. 

 Venericardia planicosta Aldrich, Bull. 1, Geol. Surv. Ala., pp. 50, 53, etc., 1886. 

 Venericardia planicosta Smith and Johnson, Bull. 43, U. S. Geol. Surv., pp. 40, 44, 45, 50, 51, 1887. 

 Venericardia planicosta Kennedy, Proc. Acad. Nat. Sci. Phila., vol. 47, p. 145, 1895. 

 Venericardia planicosta Harris, Bull. Amer. Pal., vol. I, pp. 172, 173, pi. IV, fig. 13, 1896; Bull. 



Amer. Pal., vol. II, pp. 246, 247, pis. 9, 10, 1897; Geol. Surv. Louisiana, Rept. for 1899, p. 302, 



pi. 53, fig. 6. 

 Venericardia planicosta Dall, Trans. Wagner Inst., Ill, pp. 1418-1423, 1903. 

 Venericardia planicosta Osborn, Age of Mammals, p. 93, 1910. 



Lamarck's original description. — u Venericardia (planicosta) oblique cordata, 

 crassissima; costis planis integris; posticis granulatis." 



Lamarck adds that this species is found at Grignon, France; in Piedmont, and 

 in the vicinity of Florence, Italy. 



Remarks. — Inasmuch as up to the present no true Eocene formations had 

 ever been found in the Antillean region it was thought well to figure a shell and a 

 mould of this well known and most typically Eocene species from Bed No. 2, 

 Soldado Rock. In the face of this shell which Conrad termed the " Finger post 

 of the Eocene" the writer feels confident that the Eocene age of the Soldado Bed 

 No. 2 will pass unchallenged. For this species never occurs in situ except in 

 formations of this age. 



This is the first time that Venericardia planicosta has ever been reported from 

 the Antillean region. And Soldado Rock is the only locality in that area in 

 which it has yet been found. In spite of its great known range this is the most 

 southern point from which it has ever been reported. 



Venericardia planicosta was a common species in the Soldado Rock, Bed No. 2 

 fauna, as a number of young and adult shells were obtained. The full grown 

 specimens show all the characters of this species from the southern United States. 

 When complete the greatest width of the largest shells from Soldado must have 

 been about 70 mm., while some of the young shells measure only 8. 



The migrations of this species during the Eocene were most remarkable. It 

 extends over northern France, Belgium, and England, but in Europe it is only 

 found as far south as Piedmont, in northern Italy, about 45° N. Lat. It is very 

 abundant in the southern United States, and a varietal form is even found in 

 California in the Tejon beds. Thus it had an east and west range — in a direct 

 line — of 6000 miles. Soldado Rock, about 10° N. Lat. is the furthest limit yet 

 known of its migration towards the equator. The direct North and South distance 

 from this Rock to northern Belgium is approximately 2650 miles. Dr. Dall 28 

 is persuaded that America is the center from which the group has been distributed. 



28 Trans. Wagner Inst. Science, III, pp. 1418-1423, 1903. 



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