INSTITUTE OF SCIENCE, PHILADELPHIA. 343 



Rissoina Chesneli Michaud. 



Rissoa Chesneli M\ch.3.\id, Descr. Coq. Nouv., p. 17, 1832. 

 Rissoina Catesbyana Orbigny, Moll. Cuba, ii. p. 24, pi. 2, figs, i, 3, 1842. 

 Rissoa scalarella C. B. Ads., Proc. Boston Soc. N. Hist. ii. p. 6, 1845. 

 Rissoina Chesneli Schwartz, IVIon. Rissoina, p. 73, figs. 38, 39, i860. 



Pliocene of the Catoosahatchie beds, Dall ; living from Cape Hatteras, 

 N. C, to the Antilles and Mauritius and, according to JefTreys, in the Medi- 

 terranean. 



The fossils have been compared with authentic specimens. 



Rissoina chipolana n. s. 

 Plate 22, figure 20. 



Older Miocene of the Chipola beds, Calhoun County, Florida, Burns. 



Shell slender, acute, with a minute nucleus of two and a half smooth 

 whorls, followed by seven subsequent whorls ; whorls slightly rounded, suture 

 appressed; transverse sculpture of sixteen to twenty narrow, rounded, 

 slightly flexuous ribs, usually with about equal interspaces, which completely 

 cross the whorls; spiral sculpture of fine striae, generally confined to the base 

 of the shell, but sometimes extending over the whole surface ; aperture 

 semicircular; lip thickened and varicose, produced at the middle, receding at 

 the base of the pillar and at the posterior commissure, basal fasciole obscure, 

 shghtly tumid, interior of aperture smooth and simple. Lon. of shell 6 ; 

 max. diam. 2.5 mm. 



The average size is smaller than that above given. The nearest species 

 to this is the R. triangularis Watson, a recent Australian species. The R. 

 mississippiensis Meyer has some characters in common, but is smaller and has 

 a much blunter apex; on the whole, this is a very distinct species. 



Rissoina cancellata Philippi. 



Rissoina cancellata Philippi, Zeitschr. f. Mai. 1847, P- 127. 

 Rissoa pulchra C. B. Ads., Contr. Conch., p. 14, 3850. 



Pliocene of the Caloosahatchie beds, Florida, Dall ; living in the Florida 

 Keys, the Antilles, on the west coast of South America and in the Indo- 

 Pacific region. 



Rissoina decussata Montagu. 



Helix decussata Mont., Test. Brit., p. 399, 1S03. 



Rissoa striatula Andr., Bull. Soc. G60I. de France, p. 321, 1S35. 



Rissoina striato-costata Orb., Moll. Cuba, pi. 12, figs. 30,32, 1842. 



Rissoa striosa C. B. Ads., Contr. Conch., p. 116, 1S50. 



Rissoa Janus C. B. Ads., Panama Shells, p. 53S, 1S52. 



Rissoina decussata Schwartz, Mon. Rissoina, p. So, fig. 12. 



Older Miocene of the Chipola beds, Calhoun County, Florida, Burns ; 

 Miocene of France, Italy and the Vienna basin ; Pliocene of the Caloosa- 



