49 MOLI^L'SCA OF THE GULF OF MEXICO I7 



(Scapharca) transversa Sa}- 



Arca transversa '^zx , Jour. Acad. Nat. Sci., Phila., ist. ser., 



vol. 2, p. 269, 1822. 

 transversa Conrad, Fos. Tert. Form., p. 15, pi. i, fig. 2, 

 1832 ; Tuomey and Holmes, Pleoic. Fos. S. C, p. 42, pi. 

 15, figs. 6, 7, 1856 ; Holmes, Post-Piio. Fos. S. C, p. 21, 

 pi. 4, figs. 5, 5 a; ; Gould, Inv. Mass., Binne3''s Ed., p. 

 148, fig. 465 «, 1870 ; Hilgard, House of Rep. Ex. Doc. i, 

 pt. 2, p. 887, 1 878 ; Single}', Fourth Ann. Rept. GeoL 

 Surv. Texas, p. 325, 1S92 ; Dall, Trans. Wag. Inst. Sci., 

 vol. 3, pt. 4, p. 645, 189S ; Vanatta, Proc. Acad. Nat. 

 Sci., Phila., vol. 55, p. 756, 1903 ; Clark, Pleistocene of 

 Maryland, Md. Geol. Surv., p. 206, pi. 64, figs. 7-10, 

 1906 ; Vaughan, in Matson, 2d Ann. Rept. Fla. GeoL 

 Surv., p. 149, 1909 ; Dall, in Deussen, U. S. G. S. Water 

 Supply Paper 335, p. 77, 1914 ; Dall, in Matson U. S. G. 

 S. Profess. Paper, 9S-E. , p. 177, 1916 ; Sheldon, Palseont. 

 Amer., vol. i, p. 47, pi. 11, figs. 4, 5, 6, 1916. 



Remarks. — This shell is very abundant all along the Gulf 

 coast, and is the commonest Area in the adjacent wells. 

 The specimens from the wells are often extremel}^ small, 

 3'oung forms. A Miocene variet}^ hisaria Harris, was 

 found in the Galveston well in 1895, It is more elongated 

 and less inflated than the typical form of this species. 



Distribution. — Cape Cod to Vera Cruz in 2 to 10 fms. Mio- 

 cene to Recent. Gulf coast. — Recent : Ft. Barranca, In- 

 dian Pass, Crooked Island, Florida ; Horn Island, Missis- 

 sippi ; Point a u Fer, Cameron, Louisiana; Galveston, Cor- 

 pus Christi, Texas ; Gulf of Campeachy. 



Pleistocene : New Orleans artesian well of 1856 at 41, 66, 79, 

 146, 233, 480, 570 feet ; Lake Borgne borings. New Or- 

 leans pumping station No. 7 ; New Orleans G3^mnasium 

 well at 1200 feet, Li^dia, Grand Chenier ; Knapp's wells, 

 Terrebonne Parish, No. i at 1600-1700, 2000-2150, 2250- 

 2450, No. 2 at 1050-1190, 1190-1430, 1434-1519, 1542-1632, 

 1632-1726, 1731-1739, 1780-1790, 1791-1842, No. 3 at 570- 



