296 U.S. NATIONAL MUSEUM BULLETIN 287 



silicata, Semele 1900, TWFIS, vol. 3, pt. 5, p. 987, pi. 38, fig. 6 



(Oligocene, Ballast Point, Tampa Bay, Florida); 1915, USNMB 



90, p. 154, pi. 23, fig. 7. 

 silicatus. Modiolus 1898, TWFIS, vol. 3, pt. 4, p. 793 [as tampaen- 



sis]p. 922, pi. 27, fig. 28 (Oligocene, Ballast Point, Tampa Bay, 



Florida); [as silicatus] 1905, Schuchert, Ball et al, USNMB 53, 



pt. 1, p. 412 (USNM 154349); 1915, USNMB 90, p. 127, pi. 24, fig. 



11 [corrects plate error] . 

 siUcifluvia, Marginella 1916, PUSNM, vol. 51, no. 2162, pp. 489, 



504, pi. 88, fig. 1 (Hale landing, W bank of Flint River, 7 miles SE 



ofBainbridge [Georgia]; USNM 166722). 

 silicifluvia, Pitaria (Lamelliconcha) 1916, PUSNM, vol. 51, no. 



2162, pp. 489, 500, pi. 85, figs. 2, 3 (Red Bluff, W bank of Flint 



River, 7 miles above Bainbridge, Decatur County, Georgia; 



USNM 166718). 

 silicifluvium, Cerithium 1916, PUSNM, vol. 51, no. 2162, pp. 489, 



511, pi. 87, figs. 4, 5 (Little Horseshoe bend, just below mouth of 



Blue (or Russell) Spring branch, Flint River, 4 miles below 



Bainbridge, Decatur County, Georgia; USNM 166731). 

 silicium, Bittium 1916, PUSNM, vol. 51, no. 2162, pp. 489, 510, pi. 



86, fig. 11 (E bank of Flint River, about 10 V2 miles below 



Bainbridge and above Lambert Island [Georgia] ; USNM 



166729). 

 sillana Dall and Bartsch, Odostomia (Amaura) 1909, USNMB 68, 



p. 222, pi. 28, fig. 9 (Amaknak Island, Unalaska [Alaska] ; 



USNM 168809). 

 simblus, Margarites 1913, PUSNM, vol. 45, no. 2002, p. 592 (off 



Santa Barbara channel, California; USNM 267172); [as Pupilla- 



ria simbla] 1921, USNMB 112, p. 179, pi. 18, fig. 3. 

 similaris, Lima (Limatula) 1908, BMCZ, vol. 43, no. 6, p. 408 



(ALBATROSS sta. 2799, Panama Bay; USNM 109034). 

 similaris Dall and Ochsner, Panope 1928, PCAS, ser. 4, vol. 17, no. 



4, p. 125, pi. 5, fig. 1 (Pliocene ?, E shore Indefatigable Island, 



Galapagos group; CAS 2973). 

 Simomactra 1894, N, vol. 8, no. 4, p. 40. Type-species by monoty- 



py: Mactra ( Mactrotoma) dolabriformis Conrad. 

 simplex, Venericardia 1903, TWFIS, vol. 3, pt. 6, p. 1426, pi. 56, 



fig. 12 (Eocene, Wood's Bluff, Clarke County, Alabama); 1905, 



Schuchert, Dall et al, USNMB 53, pt. 1, p. 689 (USNM 154725). 

 simplex, Volulopsiiis 1907, SMC, vol. 50, pt. 2, no. 1727, p. 164 



(USFC sta. 4792, off Bering Island; USNM 110475); 1921, 



USNMB 112, p. 90, pi. 9, fig. 1. 

 simplicissima, Pleurotomella 1907, SMC, vol. 50, pt. 2, no. 1727, p. 



140 (USFC sta. 5050, NE of Yesso, Okhotsk Sea [Japan]; 



