NATURAL SCIENCES OF PHILADELPHIA. 307 



B. Aperture merely angulated in front, with no canal, and the columella per- 



fectly plain, not twisted, frequently callously thickened above. Goniobasic 

 Section. 



3. Shell heavy, oval, oblong, or turrited, 



aperture entire above Genus Goniobasis, Lea. 



4. Aperture with a sutural, pleurotomose 



slit above Genus Schizostoma, Lea. 



C. Aperture entire and rounded in front. 



5. Shell oval, heavy, columella callously 



thickened above Genus Anculosa, Say. 



Genus 10, Lea. 



Io, Lea, Trans. Phil. Soc, iv. p. 122, 1831. Sowerby, Conch. Man. 2d Edit., 

 p. 167, 1842. DeKay, Moll. New York, p. 103, 1843. Hermannson, 

 Indicis Generum Malacozoorum, p. 562, 1846. 



Io, Lea, (sp.) Gray, Proc. Zool. Soc, pt. 15, p. 153, 1847. Jay, Catalogue, 

 4th Edit., p. 277, 1852. H. and A. Adams, Genera i. p. 299. Chenu, 

 Man. de Conchyl. i. p. 290, 1859. Anthony, Proc. Acad. Nat. Sci., p. 69, 

 1860. Reeve, Monog. Io, April, 1860. Binney, Check List, June, 1860. 

 Brot, Cat. Syst. des Melaniens, p. 29, 1862. 



Melafusus, Swainson, Malacol. p. 201, 341, 1840. Woodward, Manual, p. 

 131, 1851. 



Fusus, (sp.) Say, Jour. Acad. Nat. Sci., 1st series, v. pt. 1, p. 129, Nov., 1825. 



Mclania, (sp.) Catlow and Reeve, Conch. Nornenc, 1845. 



SPECIES. 



A. Shell smooth or only slightly tuberculate. 



1. I. flu vial i s, Say. 



Fusus fluvialis, Say, Jour. Acad. Nat. Sci., v. p. 129, Nov. 1825. Conrad, 



New Fresh Water Shells, p. 12." 

 Iofiuvialis, Say, Binney, Check List, No. 400. 

 Pleurocera fluvialis, Say, Haldeman, Iconog. Encyc, ii. p. 84. 

 Iojiuviatilis, Say, Woodward, Manual, t. 8, f. 27. Hanley, Conch. Misc., t. 



6. f. 50. Reeve, Monog. Io, t. 1, f. 5. Brot, List, p. 29. 



Io fusiformis, Lea, Phil. Trans., iv. p. 122, t. 15, f. 37. a. b. Obs., i. p. 132. 



Ravenel. Cat., p. 11. Reeve, Monog. Io, t. 1, f. 6. DeKay, Moll. 



N.Y., p. 103. Wheatley, Cat. Shells U. S., p. 28. Jay, Cat. 4th Edit. , 



p. 277. Troost, Cat. 



Jo tenebrosa, Lea, Philos. Proc, ii. p. 34, April, 1841. Phil. Trans., ix. p. 



17. Obs. iv. p. 17. Wheatley, Cat. Shells U. S., p. 29. Binney, 



Check List, No. 404. 



Io verrucosa, Reeve, Monog. Io, t. 1, f. 2, April, 1860. Brot, List, p. 29. 



2. I. inermis, Anthony. 



Io inermis, Anthony, Proc Acad. Nat. Sci., Feb. 1860, p. 70. Binney, 



Check List, No, 401. Reeve, Monog. Io, t. 3, f. 21. 

 Io lurida, Anthony, Reeve, Monog. Io, t. 3, f. 20. 



B. Shell spinose. 



3. I. s p i n o s a, Lea. 



Io spinosa, Lea, Philos. Trans., v. p. 112, t. 19, f. 79. Obs., i. p. 224. 

 Troost, Cat. Wheatley, Cat. Shells U. S., p. 29. Jay, Cat. 4th Edit., 

 p. 277. Binney, Check List, No. 402. Reeve, Monog. Io, t. 1. f. 7. 



Io gibbosa, Anthony, Reeve, Monog. Io, t. 3, f. 17. 



Io recta, Anthony, Reeve. Monog. Io, t. 3, f. 21. 



Io rhombica, Anthony, Reeve, Monog. Io, t. 3, f. 16. 



1863.] 



