TERTIARY MOLLUSCA. 



107 



Guiana is in accord with the similarity pointed out by Brown and 

 Pilsbry between H. antiguensis and other South American species. 

 The species now known from this fresh-water fauna are the following: 



Hemisinus antiguensis Brown and Pilsbry. 

 siliceus Brown and Pilsbry. 

 latus Brown and Pilsbry. 

 atrifonnis, n. sp. 



By thinella antiguensis Brown and Pilsbry . 

 Planorbis siliceus Brown and Pilsbry. 



Species from Antigua. 



List of Stations in Anguilla. T. W. Vaughan, Collector. 



6893. Crocus Bay, hill, roadside, descent to Crocus Bay from valley. 



6894. Crocus Bay, southwest side. 



6964. Crocus Bay, southwest side; fossils from rubble above shore-line. 



6965. Crocus Bay, southwest shore; fossils from lowest 10 to 15 feet of fossiliferous marls. 



6966. Crocus Bay, southwest side, 30 to 50 feet above sea-level. 



6967. Crocus Bay, bluff on southwest side, uppermost horizon, 125 feet above sea-level, 



mainly limestone. 

 6971.' Slope about 100 feet above sea-level, between Little Harbor and Pelican Point. 



The mollusks from all the localities in Anguilla, with the possible 

 exception of station 9664, which is beach rubble, appear to represent a 

 single geologic horizon. The fauna includes species common to forma- 

 tions of ages ranging from the middle Oligocene coral reef at Bain- 

 bridge, Georgia, to the Bowden marl of Jamaica, but the number of 



