87 LiGNiTic Stage 87 



Typical small specimens occur at Hatchetigbee, with strong 

 umbilical ribs, much stronger than that represented by fig. 18, 

 from Woods bluff. Larger specimens with not the slightest trace 

 of this rib are common in the Lignitic. One is represented by 

 fig. 20. 



Sometimes the ribless, more elevated, smaller specimens have 

 something of the appearance of broad varieties of A'', emiuula, 

 but a glance at the suture will distinguish the two: semilunata is 

 slightly flattened or shouldered just below the suture, while in 

 eminula there is no trace of such a character and the lower whorls 

 are tightly appressed at a small angle against the whorls above. 

 There is even a slight indentation sometimes in eminula where 

 the shoulder occurs in semilunata. 



Lignitic localities. — Ala.: Gregg's landing; Woods bluff; 3 mi. 

 s. w. of Thomasville; 4 miles above Hamilton bluff; Hatchetig- 

 bee. 



Tex.: Sabinetown. 



Type. — Lea collecftion, Acad. Nat. Sci. Phila. 



Specimens figured. — Paleont. Mus., Cornell Univ. 



Natica (Sigaticus) clarkeana, PI. 11, fig. 21. 



Syn. Sigaretiis [Sigaticus) ctai-keaniis Aid., ]r. Cinn. Soc. Nat. Hist., 



July 1887, p. 83. 

 Sigaretiis {Sigaticus) clartieanns Aid., Bull, Am. Pal., vol. i, p. 68, 



pi. 2, fig. 1 6, 1895. 

 Signatus {Eonaticina) clarkeanus Ball, Trans. Wag., etc., vol. 3, 



p. 380, 1893. 



AldricJi' s original description. — "Shell rather thick, rotnided, 

 Avhorls five, suture linear, surface of body whorl with a large 

 number of impressed lines almost obsolete in the center, but 

 numerous and distin(5l above and below; umbilicus striate within; 

 aperture lunate, inner lip covered with a callus, thickening 

 towards the posterior part. Locality: Chocftaw Corner and 

 Hatchetigbee bluff, Ala. This peculiar shell pos.sesses the form 

 of Najica, but the lines of Sigaretus.'" 



This .should not be referred to Sigaretus; its form, thick shell, 

 umbilical features are all of Natica, not Sigaretus. The faint- 

 ness of the striation on this species .sometimes suggests a close 

 relation.ship with .some forms of A^. eminula, which is generally 



