No. 6 (1921) COMMON MOLLUSCS OF SOUTH INDIA I4I 



C. litteratus and C. ceylouensis, the last with a characteristic spiral 

 white band in the middle of the mouth whorl. C. textile is a mag- 

 nificent shell, large and beautifully marked. 



Fl<;. 2*^'. Kgg capsules of a large Conusor) a broken valve of Placuna (Tulicorin). X 4. 



The Slit-lips {Pknrotomatidac) are even more numerous 

 in species than the cones and unlike them are world-wide in 

 distribution. They are fusiform in shape, with a tapered spire and 

 elongated body whorl ending in a long canal. A deep slit or 

 notch in the thin lip is their characteristic feature. Our common 

 species are P. marmorata and P. tigr'uia. 



Lastly we have the AUGER-SHELLS {Terebridae), very long 

 tapered shells of many whorls, resembling in general form the 

 Turret-shells {Tnrritella) but usually are smooth surfaced, and 

 brightly ornamented with coloured spots. Tcrebra duplicdta is not 

 uncommon in moderate depths on sandy bottom. 



Sub-Class 2.— Euthyneura. 



The gastropods belonging to this section have the visceral 

 nerve straight and not twisted as in the Streptoneura with which 

 we have just dealt. Another characteristic is the excessive develop- 

 ment of the sides of the foot into lateral folds or epipoda. These 

 tend to envelop the shell and in degree as this is more complete 

 and permanent, so the spiral form of the shell is reduced and its 

 substance lessened in thickness, till it eventually disappears. In 

 the most specialized in this direction, the torsion or twisting of the 

 body tends to disappear and the animals acquire a secondary 

 externa) symmetry. The section is divided into the orders Opistho- 

 branchiata and Pulmonata, the former marine, with breathing 

 arrangements suitable for life in water, the latter without gills and 

 normallv air-breathers, 



