173 



and having the columella truncated. The columella is moreover overlaid 

 with enamel, forming a callosity at the upper part. Those species which, 

 like our figured example M. atra, have the aperture notched above as well 

 as below, were separated by Lamarck to form his genus Pirena, but the 

 difference is not material. 



The animal of Melanopsis, according to the observations of M. Quoy, 

 is the same externally as that of Melania, and not very far removed from 

 its marine analogue Cerithium. 



1. atra, Ferussac. 



2. acicularis, id. 



3. Brasiliensis, Moric. 



4. Buccinoides, Ferussac. 



5. cariosa, Deshayes. 



6. cornea, Ferussac. 



7. costata, id. 



Species. 



8. Dufourii, Ferussac. 15. 



9. erosa, Both. 16. 



10. Esperi, Ferussac. 17. 



11. Ferussacii, Roth. 19. 



12. fusiformis, Soiverby. 19. 



13. granulosa (Pirena),Jjk. 20. 



14. Jordanica, Roth. 



labiata, Sowerby. 

 Neritaeformis, Desh. 

 nodosa, Ferussac. 

 semigranulosa, Desh. 

 spinosa, Deshayes. 

 Wagneri, Roth. 



Figure. 



Melanopsis atra. PI. 18. Fig. 99. Shell of a remarkably lengthened 

 acicular species, of the Pirena section, showing a notch at the upper 

 part of the aperture as well as at the lower. 



Genus 2. MELANIA, Lamar eh. 



Animal; dish short and slight ; head proboscis-shaped, subcorneal, 

 truncated, with the tentacles distant and subulate, having the 

 eyes on the outer side sometimes at the base, sometimes more 

 advanced ; mantle fringed. Operculum horny. 



Shell ; more or less turreted, generally wrinkled or nodulous, mostly 

 covered with a black or olive epidermis ; spire elongated, gene- 

 rally more or less eroded towards the apex ; columella smooth, 

 arched ; aperture ovate, entire, sometimes attcnuately chan- 

 nelled at the base ; lip simple. 



In this genus are brought together the very numerous series of elon- 

 gately convoluted univalve shells which inhabit the great tropical rivers, 

 chiefly of India, of the islands of the Eastern seas, and of the southern 

 States of North America. Although of that uniform dull olive-colour 



