58 Bulletin 34 go 



Geological horizon . — The shell was found at great depths at 

 a doubtful horizon where, though recent forms largel}^ 

 prevail, a slight change in the fauna appears. This leads 

 one to think that one may be approaching the Upper Mio- 

 cene. 



Occurrence. — Knapp's No. i well, Terrebonne Parish, La., at 

 2000-2150 and 2250-2450 feet. 

 (BelSuGina) amiantus Dall, Proc. U. S. Nat. Mus., 23, p. 826, pi. 

 39, f. 10, 1901 ; Tr. W. I. S., 3, p. 1386, '03 ; Vanatta, P 

 A. N. S., Phila., 55, p. 757, '03. 

 Lticina costata Holmes, Post-Pl. Fos. C, p. 27, pi. 6, fig. 2, 

 i860. Not of D'Orbigny, 1846 ; nor of Tuomey and 

 Holmes, 1857 {:=tuo7neyi Y>?^) . 

 costata Hilgard, House of Rep. Ex. Doc. i, pt. 2, p. 887, '78; 

 Dall, Bull. 37, U. S. Nat. Mus,, p. 50, '89 ; Singley, 4th 

 Ann. Rept. Tex., p. 326, '92 ; Mitchell, List Tex. Sh. 



Distribution. — N. Carolina to Sao Sebastiao, Brazil, 2-640 fms. 

 Pleistocene to Recent. Gulf coast. — Recent : Cedar Keys, 

 Ft. Barranca, Fla. ; Horn Island, Miss. ; Galveston. 

 Pleistocene : Lake Borgne borings. New Orleans artesian 

 well of 1856, at 41 and 546 feet ; New Orleans pumping 

 station No. 7; New Orleans Gymnasium well at 1200 ft., 

 Knapp's wells, Terrebonne Parish at 1600-1700, 2250- 

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

 1542-1632, 1632-1726, 1731-1739, 1780-1790, 1791-1842, No. 

 3 at 880-990, 1 040- 1 043, 1 200- 1 300, 1 330- 1 37 5, 1400- 1 440, 

 1443-1470, 1470-1480, 1500-1525, 1796-1839 feet. 



Genus D1VAR!CELLA von Martens 



quadrisulcata d'Orbigny, Voy. Amer. Mer., Moll., p. 584, 1846, 

 (as Lucina)\ Hist. Pol. y N. Isla de Cuba, 2, p. 294, pi. 

 27, f. 34-36, '53 ; Dall, Bull. 37, U. S. N. M., p. 50, '89; 

 Proc. U. S. N. M., 23, p. 815, '01 ; Trans. W. I. S., 3, p. 

 1389, pi. 51, f. I, '03 ; Vanatta,. Proc. A. N. S. Phila., 

 55> P- 757 > '03 ; Johnson, Occ. Papers, Bost. Soc. Nat. 

 Hist., 7. p. 62, 1915. 



