266 PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



for a genus whose neo-tropical representatives appear to live at high 

 altitudes. 



The two outstanding facts which characterize the distribution of 

 the genus as a whole are its occurrence in South America and its 

 non-occurrence in North America, and perhaps, of the two, the latter 

 is the more remarkable. In spite of the land connexion, more or less 

 intimate, which must have linked Europe with North America, 

 probably during the Miocene epoch, Clausilia, although abundant in 

 Central Europe, and even occurring in England, during the Eocene 

 period, did not make its way into North America. It is conceivable 

 that Clausilia was originally an inhabitant of warm climates only, 

 and that the sub-genera which now exist in the colder climates of 

 North Europe were not then developed. Marpessa,Alinda,Pirostoma, 

 and Cusmicia do not, as a matter of fact, occur earlier than the 

 Pleistocene. 



The shell of Nenia is invariably sinistral ; the aperture is rounded 

 and wide, set on a protraction, more or less pronounced, of the last 

 whorl, and lies exactly in a line with the axis of the spire. Fifty 

 species in all are known — forty-nine from the South American mainland, 

 one from Porto Rico. On the mainland they range from the Sierra 

 Nevada de Santa Martha, lat. 11° N., in the extreme north of 

 Colombia, to about 17° S. lat., in Bolivia. Along the Cordilleras 

 some species lie on the western slope, rather more on the eastern. 

 I have noted one {malleolata, Phil.) from 79° W., not 100 miles from 

 the Pacific, while the easternmost hitherto recorded lives in 63° W. lat. 

 The north and south range is thus nearly 2,000 miles, while the 

 eastern and western range is comparatively narrow. 



Nine species occur in Colombia, two in Venezuela, ene in Colombia, 

 Venezuela, and Ecuador, one in Colombia and Peru, one in Upper 

 Amazons, Peru, and ? Colombia, ten in Ecuador, twenty-one in Peru, 

 two in Bolivia, two in " South America". 



The occurrence of a single species in Porto Bico is a remarkable 

 fact, and points to a former geological connexion, more or less 

 intimate, between that island and South America. There can be 

 little doubt that the connexion was via the Lesser Antilles, and not 

 via the Peninsula of Yucatan. This view is supported by the presence, 

 in Porto Rico and in one or other of the Lesser Antilles, of the 

 genera Leptinaria, Morchia, and Peltella, all of which are South 

 American but not Central American genera. It would be interesting 

 if Nenia Avere discovered in the highlands of San Domingo, an island 

 closely connected with Porto Rico, and hitherto imperfectly explored. 



The relation of the neo-tropicalClausilias with those of thePalaearctic 

 region involves a zoological problem of the highest possible interest, 

 the solution of which is at present quite undetermined. The group 

 Laminifera, represented by one or two living species in the West 

 Pyrenees, and by six or seven species in the Miocene and Oligocene of 

 Germany, certainly exhibits points of similarity with Nenia, as was 

 shown by Bourguignat long ago. He (12) regarded the two groups 

 as standing in close relation to one another, naming the American 

 Nenia Neniastrum and the French Neniatlanta. A more prudent 



