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56 CONTRIBUTION TO THE PALEONTOLOGY OF TRINIDAD. 



Meretrix subimpressa var. golfotristensis new variety. Plate IX, Figure 9. 



Description. — A number of shells of a Meretrix were found in bed No. 8, 

 Soldado Rock, which recall the varietal form of Conrad's subimpressa, found by 

 Professor Harris in the Lignitic Eocene of Wood's Bluff, Alabama. 31 But the 

 Soldado shells when compared with the Museum specimens from Wood's Bluff 

 are seen to be smaller, less convex, more sculptured with concentric lines, and 

 with the posterior margin still more prolonged, giving the general outline of the 

 valve a more elliptical form. 



The largest specimen measures in length 20, height 10, thickness of one valve 

 3 mm. 



Locality. — Bed No. 8, Soldado Rock, Gulf of Paria (Golfo Triste of the early 

 navigators). 



Geological horizon. — Lignitic Eocene. Equivalent to the Lignitic of Alabama. 



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Genus PITARIA Romer, 1857. 



Pitaria (Lamelliconcha) circinata Born. Plate IX, Figures 12, 13. 



Venus circinata Born, Test. Mus. Vind., p. 61, pi. IV, fig. 8, 1780. 



Venus rubra Gmelin, Syst. Nat., VI, p. 3288, 1792. 



Cytherea juncea Guppy, Quart. Jour. Geol. Soc. London, XXII, p. 582, pi. XXVI, fig. 13, 1866. 



Chione circinata Gabb, Geol. St. Dom., p. 250, 1873. 



Pitaria (Lamelliconcha) circinata Dall, Trans. Wagner Inst. Science, vol. Ill, p. 1269, 1903. 



Description. — Shell subequilateral, less trigonal and more circular in outline 

 than is usual in this group, somewhat compressed; substance thin, rather deli- 

 cate; surface handsomely sculptured with close-set, regular, sharp edged, con- 

 centric lamellae; lunule small, narrowly cordate; escutcheon not defined. 



Length of shell 10, height 8.5, diameter 4 mm. 



Remarks. — Except in respect of size this shell is exactly like Dr. Guppy's 

 Cytherea juncea from Cumana, Venezuela. It is no doubt a young specimen of 

 this very interesting species. Dr. Dall says of P. circinata, "It is one of the 

 very small number of Veneridce which occur on both the Atlantic and Pacific 

 coasts of middle America, and in harmony with this exceptional distribution also 

 occurs in the Isthmian Oligoeene." 



This species has remained practically unchanged from Oligoeene to recent 

 times. It is akin to the characteristic Lower Oligoeene P. imitabilis Conrad 

 from Vicksburg, Mississippi. 



P. circinata has been reported from the Oligoeene of Panama (Gatun beds) 

 and of Cumana, Venezuela; from the Pliocene of Trinidad; and is living on both 

 coasts of Central America and in the Antilles. 



Locality. — Along the shore 1000 feet west of the pier at Brighton, Trinidad, 

 in an impure asphalt. 



Geological horizon. — Upper Oligoeene. Equivalent to the Chipolan stage of 

 Florida. 



81 See Bull. Am. Pal., vol. II, p. 255, pi. 12, figs. 6, 7, 1897. 



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