20 Calvin Goodrich 



Gyrotoma cxcisum (Lea) 

 PI. II, figs. 22 and 23 



Melania excisa Lea, Proc Amer. Phil. Soc, II, 1843^ p. 242; Trans. Amer. Phil. 

 Soc, IX, 1844, pp. 25, 29; Trans. Amer. Phil. Soc, X, 1848, p. 93; Obs. Gen. Unio, 

 IV, 1848, pp. 25, 29, 93; Jay, Cat, 4th ed., 1852, p. 273. 



Schizostoma excisa Lea, Wheatley, Cat. Shells U. S., 1845, p. 28 ; Lea, Journ. Acad. 

 Nat. Sci., Phila., V, n. s., 1862, p. 250; Obs. Gen. Unio, IX, 1863, p. 72; Lewis, Amer. 

 Journ. Conchol., V, 1869-70, p. 168; Tryon, Monog. Strepom., 1873, pp. xv, xxiii, xxv. 

 356; Lewis, Fauna of Ala., 1876, p. 23. 



Gyrotoma excisa Lea, H. & A. Adams, Genera, I, 1858, p. 305 ; Binney, Check 

 List, i860, No. 317; Brot, List, 1862, p. 27; Paetel, Cat., 1888', p. 362. 



Gyrotoma olivula excisa (Lea), Hannibal, Proc. Malacol, Soc, X, 1912, p. 181. 



Melatoma excisum Lea, Reeve, Monog. INIelatonia, i860, sp. 2. 



Melatoma Showalterii Lea (prob. excisum), Reeve, Monog. Melatoma, 1861, sp. 23. 



Gyrotoma ovoideum Shutt., Mittheil, Bern. Nat. Gesell., No. 50, July 22, 1845, p. 

 88 ; H. & A. Adams. Genera. I, 1858. p. 30n. pi. 32. fig. 4 ; Paetel, Cat.. 1888, p. 362. 



Schizostoma ovoideum Shutt., Tryon, Monog. Strepom., 1873, PP- ^'^'. 3r>6 ; Lewis, 

 Fauna of Ala.. 1876. p. 23; Hinkley. Nautilus. XVIII, 1904, p. 41. 



Gyrotoma bulbose Anth., Proc. Acad. Nat. Sci., Phila., Feb. i860, p. 65 ; Binney, 

 Check List, i860. No. .309; Brot, List. 1862. p. 27; Paetel, Cat., 1888, p. 361. 



Melatoma bulbostim Anth., Reeve, Monog. Melatoma, 1861, sp. 22. 



Schicostoma bulbosum Anth., Lewis, Amer. Jour. Conchol., 1869-70, p. 168; 

 Tryon, Monog. Strepom., 1873, P- 361 ; Lewis, Fauna of Ala., 1876, p. 22. 



Gyrotoma ovalis Anth., Proc. Acad. Nat. Sci., Phila., Feb., i860, p. 65 ; Binney, 

 Check List, i860. No. 325; Brot, List, 1862, p. 27; Paetel, Cat., 1888, p. 362. 



'Schizostoma glans Lea, Proc. Acad. Nat Sci., Phila., i860, p. 186: Journ, Acad. 

 Nat. Sci., Phila., V, n. s., 1862, p. 248, pi. 35, fig. 52; Obs. Gen. Unio, IX, 1863, pp. 70, 

 71, 74, pi. XXXV, fig. 52; Lewis, Amer. Journ. Conchol., V^ 1869-70, p. 168; Tryon, 

 Monog. Strepom., 1873, p. 363 ; Lewis, Fauna of Ala., 1876, p. 23 ; Hinkley, Nautilus, 

 XVIII, 1904, p. 40. 



Gyrotoma glans Lea, Binney, Check List, i860. No. 320; Brot, List, 1862, p. 2/. 



Melatoma ellipticum Anth., MSS., Reeve, Monog. Melatoma, 1861, sp. 21. 



Gyrotoma ellipticum Anth., Brot, List, 1862, p. 27; Paetel. Cat., 1888, p. 362. 



Schizostoma ellipticum Anth., Lewis, Amer. Journ. Conchol., V, 1869-70, p. 168; 

 Tryon, Monog. Strepom., 1873, p. 359; Lewis, Fauna of Ala., 1876, p. 2s; Hinkley, 

 Nautilus, XVIII, 1904, p. 40. 



Description: Shell striate, subfusiform, rather thick, yellowish; spire ovately 

 conical; sutures impressed; whorls flattened; aperture cut out above, small, elliptical, 

 white. 



Habitat : Alabama. 



Diameter, .40; length, .64 of an inch. — Lea. 



As variation goes in Gyrotoma this species is remarkably wanting in 

 variability. At Wetumpka it bears folds in common with many other Pleu- 

 roceridae there and at Three-Island Shoals, the other extreme of its occur- 

 rence, it is ordinarily lighter in color and smooth. Otherwise there is little 

 difference between the members of the two colonies. This may argue that 

 excisum is the oldest of the genus, time having brought its usual uniformity, 

 and this hypothesis is supported by the fact that the species has the longest 

 range of all Gyrotomae. 



The fissure is deep, up to 10 mm., in the largest adults, very narrow in 

 the young and widening with age; ordinarily straight, but in a few shells 



