Thk Genus Gyrotoma • 17 



Description : Shell conic, thick, dark brown ; spire obtusely elevated, truncate, 

 though not abruptly so, six whorls remaining, one or two having apparently been lost 

 by truncation ; carinations elevated, subacute and found on all the whorls, two on 

 each of the spiral ones and three or four on the body whorl ; fissure direct, broad and 

 moderately deep, extending about one-fifth around the shell; sutures irregular, much 

 modified by the carinae, and often concealed in part by them ; aperture ovate and band- 

 ed within; columella much rounded, callous at the lower part only; outer lip irreg- 

 ularly waved, its outline modified by the carinae on the bod3'-whorl; no sinus. 



Habitat : Coosa River, Alabama. 



Length of shell, 7-8; breadth of shell, 1-2 of an inch. Length of aperture, 55^-l6 

 of an inch; breadth of aperture, 1-4 of an inch. — Lea. 



The opportunity has been given to examine the type of cariniferum, 

 which is in the Museum of Comparative Zoology. The shell is about three- 

 fourths grown. The fissure is rather narrow as compared with the same 

 character in several other species, is slanting and 8^^ mm. deep. In twenty- 

 five other specimens the fissure of seven is straight, very slightly oblique in 

 one and noticeably oblique in seventeen. The girdle is narrow and of much 

 the same color as the body of the shell. 



Full grown specimens are not so stoutly ribbed as younger ones, and 

 in instances the folds become almost obsolete. A few greatly resemble G. 

 alubamensis Lea. The largest shell measured 24 x 15 mm. It should be 

 said that in the cut published by Tryon (10, p. 353) the ribs are made to 

 seem more twisted than they actually are in the type. The color is brown- 

 ish olive. The banding formula, common to the group, is four bands, the 

 third from the top being smaller than the rest. Variations occur, but they 

 are modifications of this formula. The aperture is more often elliptical 

 than ovate. In old specimens the columella is white, wide, continuous and 

 with the usual node of porcelain-like callus at the top. Young shells are 

 angtilated at the base. They indicate that an uneroded adult would have 

 eight whorls. 



The only locality known for this species is Fort William Shoals. In 

 1914, shortly after a visit to this site, i\Ir. Smith wrote to Dr. Walker. "On 

 a reef * * * I struck G. cariniferum; the only ones I had seen before 

 were a broken specimen in the Schowalter collection and about ten I had 

 collected last year in a lower part of Fort William Shoals. In this new 

 place we gathered about 200 in three hours, and I think we scraped the place 

 nearly clean. The species occurred only in about fifteen yards of the reef 

 and always in the swiftest water where other Gyrotoma cannot stick. There 

 was one little pool under a fall which must have yielded over 100 fine ones." 



Hinkley (2, p. 41) mentions showalterii Lea. It is not clear that he re- 

 fers to the species which has had to give way to carinifermn by reason of 

 the rule of priority or to the one given the same name by Lea in 1864. 



Group of Gyrotoma lezvisii 



Elongate to ventricose, the whorls almost flat, sometimes ligulate, the 

 shell rather heavy and resembling Goniobasis impressa Lea in sculpture; 

 fissure oblique, with a maximum depth of 6 mm.; girdle not pronounced; 

 aperture narrow ; the sinus distinct ; bands consisting usually of many fine 

 lines. 



