GASTEROPODA. 
135 
TURBO, Linn/eus. 
Turbo Shumardii. 
PLATE XXIX, FIGS. 1-4. 
Turbo Shumardii, de Verne oil. 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. 
