lo Calvin Goodrich 



Gyrotoma laeta incisa (Lea), Hannibal, Proc. Malacol. Soc, X, 1912, p. 182. 

 Schicostoma pyramidatum Shutt., Tryon, Monog. Strepom., 1873, pp. xv, 365; 

 Lewis, Fauna of Ala., 1876, p. 2Z. 



Description: Shell pyramidal, heavy, olivaceous or blackish, concentrically sul- 

 cate-costate, more often with rough knobs (nodules) ; banded with brown, apex 

 eroded; whorls S or 6; fissure short, broad, columella thickened tuberculously above. 



Length, .9; breadth of the ultimate whorl, .412-.5 of an inch. Length of aper- 

 ture, .312; length of fissure, .1 of an inch. 



Obs. — Somewhat resembles Melania canaliculata; varies as the preceding {G. 

 oroide a). 



A few specimens . . . occur among others, with the upper whorls acutely 

 carinated, ridges and furrows fewer and almost obliterated; epidermis paler and apex 

 little eroded. — Shuttleworth. 



This is the first Gyrotoma appearing in the river. Mr. Smith's highest 

 station for it was Lock 2, which is at the head of Ten-Island Shoals, between 

 St. Clair and Etowah counties. Shuttleworth in his preface states that 

 Rugel collected in the Coosa River, near Wetumpka. But there is sound 

 reason for believing that this is an error. The species was never taken by- 

 persons who collected from Wetumpka as far up the stream as Fort 

 William Shoals. The nodulous character of the shells sent to Europe is a 

 peculiarity almost entirely confined to Pleuroceridae upon and near Ten- 

 Island Shoals. Not only are the Gyrotomae of this locality so marked and 

 the so-called Eurycaelon, but also Anculosae and Goniobases. In a letter to 

 Dr. Walker, Mr. Smith said that even certain Pleurocerae are likewise 

 affected. The oddity is not in mollusks collected farther up the river. It 

 tends to disappear below these shallows. 



The fissure^ is shallow, oblique, and is angled rather than curved or 

 sinuous as in inciswm, also having a short fissure. At Lock 2, the fissure 

 has a maximum depth of 3 1-2 mm. At Hall's Island, it is as deep as 5 

 mm. and is not so oblique as in material from the higher locality. Oblique- 

 ness is more pronounced in young specimens than in old; in juveniles the 

 fissure is a mere notch. The hem is only faintly marked, being of much 

 the same color as the rest of the shell ; it is to be observed in hardly more 

 than half the shells. 



The pyramidal aspect is that mostly of individuals one-half to three- 

 fourths grown. The base is usually rounded in adults. Knobs, when pres- 

 ent, give the shell a squared, four or five-sided appearance, and are not 

 spaced regularly. Color- ranges from honev-yellow to raw-umber. The 

 prevailing banding formula is four bands of equal width. The aperture 

 is ovate. The white or bluish-white columella is smoothly rounded, slightly 



^In the literature of Pleurotomariidae the fissure is spoken of as the "anal sinus" 

 and the girdlei or hem as the "sinus band". I have preferred to use the terms of the 

 early writers upon Gyrotoma even if the others be more descriptive. Doubtless as in 

 the marine mollusk the fissure of Gyrotoma serves a purpose for the discharge of 

 excreta. 



^The colors assigned in this study are according to "Color Standards and Color 

 Nomenclature" of Ridg\vay, 1912. While a fairly large number of names have been 

 given in order to be as exact as possible it will be remarked that the color range* in 

 this genus is rather limited. 



