1. apiata, Guillou. 



2. atra, Reeve. 



3. Bourgainvillei, Recluz. 



4. depressa, Lesson. 



5. D'Urvillei, Recluz. 



158 

 Species. 



7. Freycineti, Recluz. 



8. Janelli, id. 



9. La Perousei, id. 



10. lineata, Lam. 



11. Luzonica, Soul. 



13. porcellana, Desk. 



14. radiata, Reeve. 



15. Recluzii, irf. 



16. suborbiculata, $M0. 



17. Suffreni, Recluz. 



6. Entrecastauxi, id. 12. macrocephala, G^«7^. 18. tessellata, Lam. 



Figures. 



Navicella poecellana. PL 16. Fig. 82. Shell, showing at Fig. a its 

 widely dilated aperture, lateral muscular impressions, transverse 

 septum and inconspicuous spire, and at Fig. b its external variegated 

 painting covered with a dark olive epidermis. — From Mr. Cuming's 

 collection. 



Genus 2. NERITINA, Lamarck. 



Animal ; disk triangularly ovate, truncated and thicker towards 

 the front, bearing about the middle a peculiar semilunar calca- 

 reous operculum ; head large, but little projected, furnished 

 with a dilated labial appendage and having four tentacles, two 

 long and subulate, two short and truncated, on which are situ- 

 ated the eyes. 



Shell ; ovately globose, with the spire very short and indistinct, 

 and the whorls sometimes armed with hollow spines ; columella 

 depressly flattened into a transverse septum, aperture semicir- 

 cular, lip simple, sometimes dilated on either side; outer 

 surface mostly covered with a dark epidermis. 



The Neritina or Fresh- water Nerites are more stoutly convoluted than 

 the NavicellcB, and form an interesting link between them and the Nerita 

 of still more solid growth, inhabiting the sea. There is little difference in 

 the animal beyond that resulting from their different circumstances of 

 habitation. The Neritince dwell principally on the banks of rivers, and 

 are not unfrequently found upon palms and other nuviatile plants. 



Few species of this extensive genus present any variation of sculpture 

 beyond a slightly plicated or granulated surface, with the exception of 

 some which are coronated with a row of hollow spouted spines, short as in 



