376 LAND AND FRESH-^VATER SHELLS OF N. A. [PART IV. 



24. S. salebrosum, Anthony. 



Gyrotoma salebrosa, AxTHONT, Proc. Acad. Nat. Sci., p. 66, Feb., 18G0. Binkey, 



Check List, No. 333. 

 Melatoma salebrosum, Anthony, Reeve, Monog., sp. 8 and 15. 

 Gyrotoma robusta, Anthony, Proc. Acad. Nat. Sci., p. C7, Feb., 1860. Binney, 



Clieck List, No. 332. Brot. List. p. 28. 

 Melatoma robustum, Anthony, Reeve, Monog., sp. 14rt, b, 

 Melatoma rectum, Anthony, orf Reeve, Monog., sp. la. 



Description.— Shell fusiform, robust, thick, nodulous, of a dusky 

 olive-color; spire truncated, leaving scarcely more than the body- 

 whorl, but indicating by traces on the truncation the loss of three or 

 four others; fissure moderately open, waved, not deep; body-whorl 

 roughly nodulous at the upper part and ornamented by three dark 

 Fi". 708. bands below ; aperture ample, ovate, dusky within 

 and banded by three broad bands; columella deeply 

 rounded, covered with a thick deposit of callus, 

 white at its lower portion, but tinged with dark brown 

 at the fissures. 

 Habitat. — Coosa Elver, Alabama. 

 Length of shell, three-fourths; breadth of shell, one-half of an 

 inch. Length of aperture, niue and one-half sixteenths ; breadth of 

 aperture, five-sixteenths of an inch. 



Observations. — This species presents the unusual characteristic of a 

 nodulous surface, which character has not been observed in any spe- 

 cies hitherto described by any American author. These nodules are 

 very conspicuous and much compressed laterally, so as to present very 

 much the appearance of coarsely folded ribs. — Anthony. 



The nodules, or rather folds of >S'. salebrosum, by which 

 Mr. Anthony distinguishes it from S. robustum are caused 

 by the arrest of growth and indicate the position of former 

 mouths of the shell. 



The type of S. robustum (which I figure) is a more than 

 usually smooth variety, but I have before nie a number of 

 specimens, which exhibit the intermediate stages between it 

 and the folded S. salebrosum. 



Mr. Reeve's fig. 7a, intended for S. rectum, is, I think, ref- 

 erable to this species. 



Mr. Lea's incisum is not the same as salebrosum, as he sup- 

 poses, but is quite a different sliell in form. 



The following is Mr. Anthony's description of 



