94 BULLETIN 90, UNITED STATES NATIONAL MUSEUM. 



Family MODULIDAE. 



Genus MODULUS Gray. 



Modulus Gray, Synopsis Brit. Mus., 1842, pp. 60, 90, (name only) ; Proc. 



Zool. Soc. London, for 1847, p. 150. — Dall, Trans. Wagner Inst., vol. 

 3, pt. 2, p. 293, 1892. Monotype, Trochus modulus Linnaeus. 

 Turbinopsis Conrad, Journ. Acad. Nat. Sci. Pliila., ser. 2, vol. 4, p. 2S9, 



March, 1860. Type, T. hilgardi Conrad, Cretaceous of Mississippi. 

 Pseudotrochus Heilprin, Trans. Wagner Inst., vol. 1, p. 114, 1887 ; not of 



Klein. 



This genus has existed in America since the era of the Cretaceous, 

 and it is somewhat remarkable that it has so few recent species as 

 descendants. 



MODULUS TURBINATUS Heilprin. 



Plate 15, fig. 7. 



Pseudotrochus turbinatus Heilprin, Trans. Wagner Inst., vol. 1, p. 114, 



pi. 16, fig. 57, 1887. 

 Modulus Uirhinatus Dall, Trans. Wagner Inst., vol. 3, pt. 2, p. 294, pi. 18, 



fig. 12, 1892. 



Tampa silex beds at Ballast Point, Florida; Heilprin and Dall. 

 U. S. Nat. Mus. No. 165110. 



This is, perhaps, the finest and largest species of the genus. 



Family LITTORINIDAE. 

 Genus LACUNA Turton. 



Lacuna Turton, Zool. Journ., vol. 3, p. 190, Oct. 1827. Type, Helia; 



lacuna Montagu. 

 Lutea Brown, 111. Brit. Conch., Dec. 1827, expl. pi. 46, figs. 50-53; Helix 



lutea and H. lacuna Montagu. 

 Epheria Leach, Moll. Gt. Brit. 1852, p. 192, pi. 9, fig. 3; Turbo vincta 



Montagu ? 

 Temina Leach, Moll. Gt. Brit. 1852, p. 182; fig'd sp. Lacuna puteolus 



Forbes and Hanley. 

 Medoria Leach, Moll. Gt. Brit. 1852, p. 196, Ttirbo crassior Walker, first 



species. 



For Lacuna Turton named no type, but Helix lacuna Montagu 

 would by the rules be taken as the homonym, and was so taken by 

 Herrmannsen in 1847, though Gray, in the same year, suggested 

 Turton's first species, L. pallidula. 



LACUNA PRECURSOR, new species. 



Plate 12, fig. 5. 



Shell small, smooth, turbinate-conic, with about 4 well rounded 

 whorls separated by a deep suture ; apical whorl very small and flat- 

 tened above, the others almost inflated, regularly increasing, with 



