HELIX-AMPELITA. 17 



Group of H. sepulchral Per. Globose-depressed, carinated or 

 rounded ; upper lip of aperture broadly expanded and reflexed ; 

 basal lip narrower, reflexed. 



Group of H. omphalodes Pfr. Depressed, often bluntly angled 

 but not acutely keeled ; peristome narrowly expanded and reflexed 

 all around, scarcely more widely above than below. 



Group of H. xystera Val. Periphery acutely keeled ; peristome 

 narrowly expanded all around, or not at all expanded above. 



Group of If. lanx Fer. Shell large, depressed, usually malleated ; 

 umbilicus decussated inside ; peristome narrowly reflexed below, 

 upper margin scarcely expanded. 



Group of H. duvallii Petit. Depressed ; rounded or not acutely 

 keeled ; umbilicus moderate ; peristome narrowly expanded all 

 around, blunt ; parietal callous heavy. 



Species not grouped, including a number of diverse forms not seen 

 by me, which do not seem to belong to any of the foregoing groups. 



NOTE ON THE PHYSICAL FEATURES OF MADAGASCAR. This great 



island, says Wallace, is situated about 250 miles from the east coast 

 of Africa, and extends from 12 to 25 S. lat. It is almost exactly 

 1000 miles long, with an extreme width of 360 and an average width 

 of more than 260 miles. A lofty granitic plateau, from 80 to 160 

 miles wide, and from 3000 to 5000 feet high, occupies its central por- 

 tion on which rise peaks and domes of basalt and granite to a height 

 of nearly 9000 feet. There are also numerous extinct volcanic cones 

 and craters (Island Life, p. 377). 



The central elevated region is surrounded by extensive plains, ly- 

 ing much lower, and widest to the west and south. It is encircled 

 by a continuous zone of dense forest, from six to fifty miles wide, 

 and except in the northeast, about thirty miles inland. The entire 

 island is well watered. The rivers are numerous but small. Many 

 of those on the eastern slope cutting their way in magnificent gorges 

 through the ramparts of the inland plateau. . 



Section AMPELITA s. s. 

 Group of H. sepulchralis Fer. 



These shells have the upper part of the lip very broadly expanded 

 and reflexed, much broader than the basal margin. Most of the 

 2 



