8 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



islands, as far as known, intervening between Mindoro and Luzon 

 or Panay. 



The group of A. chloris, embracing roeseleri and sulitenis, extends 

 over the Sulu Archipelago and Zamboanga, Mindanao, and it appears 

 as if it had been derived from Borneo and had reached Mindanao 

 through the chain of islands which extend from Borneo to Mindanao, 

 through Tawi Tawi, Jolo, etc. 



Amphidromus i?iflatus, pallidulus, mearnsi, and calista are yellow 

 forms which, though the last is at times variously marked with red, 

 combine the yellow coloration of the chloris group with the black 

 filations of maculiferus. 



By far the most satisfactory lot of material which we have had for 

 our study belongs to the group of Amphidromus maculiferus, which 

 divides up into a series of geographic races, beautifully accounted for 

 by the separate habitats Avhich they occupy. A full discussion of 

 this group will be found preceding the description of this species 

 and its races. 



I wish to acknowledge my deep appreciation of the courtesies ex- 

 tended to me by the authorities of the United States Bureau of 

 Fisheries and the United States National Museum, in assigning the 

 collection of mollusks made by the Fisheries steamer Albatross in 

 the Philippines, to me for report. Also to the Philippine Bureau of 

 Sciences for material sent for report, and to Dr. H. A. Pilsbry, of 

 the Philadelphia Academy of Natural Sciences, for the loan of the 

 Philippine Amphidromi in the collection of the academy, and to 

 Dr. Frank C. Baker, of the Chicago Academy of Sciences, and 

 Walter F. Webb, of Rochester, New York, for similar reasons. I 

 wish also to express my sincere thanks to Dr. William H. Dall, 

 honorary curator of the Section of Mollusks, United States National 

 Museum, for his counsel and many suggestions. 



The photographs used in the illustrations were made b}* the Divi- 

 sion of Photography, United States National Museum, and were 

 retouched by Mrs. E. B. Decker. 



GROUP OF AMPHIDROMUS MACULIFERUS. 



The group of Amphidromus maculiferus extends over the south- 

 eastern islands of the archipelago, its chief center being Mindanao. 

 When one looks at a topographic or relief map of the Philippine 

 Islands, particularly Mindanao, one sees that this island is composed 

 of a series of smaller islands which have been fused into the large 

 territory by a comparatively moderate raising of that part of the 

 ocean floor, and the Amphidromi reflect this state of affairs beau- 

 tifully. 



Amphidromus maculiferus Sowerby ss. was described from ma- 

 terial collected by Hugh Cuming in Misamis Province, Mindanao, 



