BULIMULUS-NAESIOTUS. 101 



Bulinus mix BROD., P. Z. S., 1832, p. 125 (Charles Id.); SBY., 

 Conch. Ill, p. 6, figs. 37, 37*, 1833. Bulimus nux DESK, in Lara. 

 An. s. Vert., ed. ii, vol. viii, p. 276, 1838. PFR., Mon. Hel. Viv., II, 

 p. 183, 1848. REEVE, Conch. Icon., pi. xxiii, fig. 150 (not typical) ; 

 SMITH, P. Z. S., 1877, p. 72. Buliminus nux BECK, Ind. Moll., p. 70, 

 1838. Bulimus (Ncesiotus) nux ALBERS, Heliceen, p. 162. Buli- 

 mulus (Omphalofityld) nux H. & A. ADAMS, Gen. Rec. Moll., II, p. 

 161, 1855. Bulimulus (Nesiotes) nux MARTENS, in Albers ed II, p. 

 220, 1860. Bulimulus (Ncesiotus') nux PFR., Norn. Hel. Viv., p. 254, 

 1881. Bulimus nuciformis PETIT, Journal de Conchyl., IV, p. 365, 

 pi. xi,fig. 7, 1853. PER., Mon. Hel. Viv., IV,p. 410,1859. Bulimus 

 (Ncesiotus) nuciformis PFR., Mai. Blatt., ii, Vers., p. 161, 1854.- 

 Bulimulus (Nesiotes) nuciformis MARTENS in Albers, ed. ii, p. 220, 

 1860. Bulimulus (Ncesiotus) nuciformis PFR., Norn. Hel. Viv., p. 

 254, 1881. Bulimus incrassatus PFR., P. Z. S., 1852, p. 157; in 

 Chemn, Conch. Cab., ed. ii, Bulimus, 79, pi. 30, figs. 13, 14; Mon. 

 Hel. Viv., Ill, p. 415, 1 S53. Bulimulus (Omphalostyla) incrassatus 

 H. & A. ADS., Gen. Rec. Moll., II, p. 161, 1855. Bulimulus unifas- 

 ciatus REIBISCH (non Sby.) Isis, 1892, p. 32, pi. i, fig. 1, not p. 15. 

 Bulimulus (NceMotus) nux REIBISCH, Isis, 1892, p. 15. Bulimulus 

 (Ncesiotus*) incrassatus REIBISCH, Isis, 1892, p. 16, t. i. fig. 4a ; var. sul- 

 catus REIB., Ibid. p. 16, t. i, figs. 4b c ; var. nuciformis REIB., Ibid., p. 

 16, t. i, fig. 4d. Bulimulus (Ncesiotus} nux STEARNS, Proc. U. S. Nat. 

 Mus., xvi, pp. 376-381, 425, 426, 1893. DALL, Proc. Acad. N. S. P., 

 1896, p. 429, pi. 16, f. 6 (genitalia), pi. 17, f. 10 (dentition). 



Type of the section Ncesiotus. B. nuciformis Petit is practically 

 a typical n ux ; while Reeves' nux (pi. 16, figs. 33), is a rather 

 heavier form with quadrate aperture and thick lip. 



" The synonymy exhibits, almost as clearly as the specimens, the 

 great variability of this species. The facts also seem to indicate 

 quite positively that a great proportion of this variability in this 

 instance is due quite as much to an intrinsic tendency to vary in the 

 matter of color and form as to any direct influence of the environ- 

 ment promoting by special circumstances any special variation. At 

 least, while it is not questionable that some of the variations might 

 easily be made permanent by natural selection, it is probable, as 

 yet, that matters have not reached that stage, since the evidence of 

 collectors seems to establish the fact that the different variations of 

 color and form are found indiscriminately in the same region and 

 under the same conditions. Further and more precise observation 



