CHAPTER XVII: THE NOTCH-SIDE SHELLS 



Family Pleurotomid/€ 



Genus PLEUROTOMA, Lam. 



Shell spindle-shaped, with anterior canal of more or less 

 length; aperture oval ; lip thin, notched near the suture; opercu- 

 lum usually present, horny, annular; head broad; tentacles wide 

 apart, with eyes at base; siphon long; mantle border notched 

 below notch in shell ; radula present ; teeth long, hollow, connected 

 with poison gland. A large family of little known shells found in 

 all seas. 



The spindle-shaped shell, drawn out at both extremities, 

 has the tell-tale anal slit, or notch, in the outer lip near its junc- 

 ture with the spire. By this sign we know them. Some have 

 the anterior canal short, but the spire is always elongated. Reeve 

 lists 369 species. Many of these are described from single speci- 

 mens, so the number is probably far too great. 



The Great Notch-side {P.grandis,Gra.y), the largest species, 

 is six inches long; its greatest diameter is about one inch. In 

 this graceful spindle-shaped shell one sees the notch-sides at their 

 best. The whorls are delicately chiselled in many sharp revolving 

 ridges, with fine raised striae between. Broken longitudinal and 

 spiral lines of brown handsomely decorate the yellowish exterior. 

 The finest and closest dots follow the sutures. 



Habitat. — China Seas. 



The White Notch-side (P. T/rgo, Lam.) shows a glossy white 

 surface where the horny epidermis is removed. Its whorls are 

 deeply cut into ridges, the central one forming a strong keel. 

 A series of these shells exhibits considerable variation. The 

 spire is in every case longer than the canal. The name "White 

 Tower of Babel," has been given thisspecies. Length, 3 to 4 inches. 



Habitat. — West Indies. 



Carpenter's Notch-side (P. Carpenteriana, Gabb.) has a 

 regular spindle shape, tapering gracefully to base and apex. 



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