210 PROCEEDINGS OF THE ACADEMY OF [Mar., 



tured surfaces. Where the sea had been eating into the cliff, and 

 detaching slabs of the hard, flinty layers, the surfaces of these flint 

 slabs were completely covered with the flint pseudomorphs of the 

 shells, these in most cases having the finest sculpture perfectly 

 preserved. The relation of these beds to the other members of 

 Browii's division 3 as given in his Notes on the Geology of the Island of 

 Antigua is shown in the section of the rocks at Dry Hill, on page 595,* 

 and there it will be seen that the lacustrine or fresh-water chert layers 

 immediately overlie the Volcanic Sands which form the lower 

 23+ feet of the section. The same sequence of deposits is also 

 seen at Corbizon Point, where the fresh-water chert layers with silicified 

 wood occur along the shore immediately above these same Volcanic 

 Sands that are found at Dry Hill. Near the Botanic Station, just 

 east of St. John's, the flinty layers with fresh-water shells are found, 

 but the shells are imbedded in the flint and only show in sections 

 in the hard, compact rock. The reddish beds of the Volcanic Sands 

 are absent at this locality east of the Botanic Station or are only 

 represented by sandy nodules in the white tuffs. No silicified wood 

 was seen at this place. 



The species described below belong to the genera Hemisinus, 

 Bythinella, and Planorhis. The genus Hemisinus is undoubtedly 

 what Purves has called Melania and indeed he mentions Hemisinus 

 as being found living in Cuba. These species of Hemisinus are 

 described below. The Bythinella is probably what Purves referred 

 to Nematura or Amnicola; we have described one species. The one 

 Planorhis which we describe is the only representative of this genus 

 in the collection. We found no representatives of Melampus, Trun- 

 catella, Pomatias, Zonites, and Neritina, mentioned by Purves. 

 Hemisinus antiguensis n. sp. PI. IX, figs. 1, 3, 5, 6. 



The shell is slender, diameter contained nearly three times in the 

 length; whorls rather numerous, probably at least fifteen in a perfect 

 shell, as a young one 12.5 mm. long has twelve whorls, the upper 

 part of the spire being very slender. Whorls convex, sculptured 

 with many rounded ribs, as wide as their intervals, somewhat curved, 

 the concavity forward and somewhat protractive. There are about 

 25 ribs on a whorl. Above the lower suture of each whorl there are 

 two or three spiral cords, the lower one strongest. ( )n the last whorl 

 the ribs extend to the periphery where they disappear, the peripheral 

 region and the base having numerous spiral cords. The aperture 



' Brown, loc. cit. 



