GASTEROPODA. 13 5 



TURBO, LiNNiEus. 

 Turbo Shumardii. 



PLATE XXIX, FIGS. 1-4. 

 Turbo Shumardii, de Verneuii. Bulletin de la Soc. Geol. de France. 



Shell gibbous, subglobose. Spire moderately elevated, apex minute ; volutions 

 about five or six, gradually enlarging in the earlier stages of growth, and 

 the last one becoming extremely ventricose, with a broadly expanded 

 aperture : the earlier volutions are smooth and regularly rounded upon the 

 exposed surfaces, gradually becoming nodose and flattened or somewhat 

 concave upon the upper side, the nodes increasing in size and strength 

 with the increase of the volutions. Suture close in the earlier volutions, 

 and becoming somewhat canaliculate in the later ones. Lower side of 

 the outer volution very convex, even in the umbilical region, and much 

 extended in the direction of the columella. Aperture broadly rounded 

 or somewhat obscurely pentahedral : columellar lip obtuse, thickened, 

 having a distinct broad opercular groove ; callus covering the umbilicus 

 and spreading outwardly; external margin of the aperture thin. 



Surface marked by fine, comparatively even striae of growth, which are often 

 crowded in fascicles, and in old shells are somewhat imbricated at irregular 

 intervals. Periphery of the outer volution with a strongly elevated 

 obtusely angular carina, which is continued from the suture-line at the 

 inner posterior angle of the aperture. The outer one or two of the 

 volutions (depending on the size of the shell), marked by strong curving 

 nodes, which, commencing just below the suture, are nearly vertical 

 for a short distance, and then curving forward are finally directed towards 



the aperture, and gradually become merged in the general surface.* 



—  — - —  '  — — — # — 



* This feature is not constant. In some specimens the nodes, after turning forward, are continued ver- 

 tically in a low elevation till they invade the peripheral carina, giving it a subnodose character, as seen in 

 the lateral view of the larger specimen on plate 29. In the older shells the carina becomes subdued and 

 rounded in outline. 



