1904.] NATURAL SCIE^■CES OF PHILADELPHIA. 809 



NEW CLAUSILIID^ OF THE JAPANESE EMPIRE— X. 

 BY HENRY A. PILSBRY. 



In this tenth^ article upon Japanese Clausiliidce, the species discov- 

 ered by Mr. Nakada in the Ryiikyu Islands and by Mr. Azuma in 

 Satsiima and its islands, are dealt with, together with a few forms from 

 other parts of the empire. The two collectors mentioned, working 

 under ^Ir. Hirase's direction, have about doubled the number of land 

 mollusks known from the Ryukyu Islands. Tokunoshima has proved 

 particularly rich. The transition from the Ryukyuan fauna to that 

 of Japan proper is found in Yakujima and Tanegashima, Osumi, and 

 in the Koshikijima group, south of Satsuma. In these islands there 

 is a strong Ryukj^ian strain, but the Kyushu faunal element predomi- 

 nates. 



In the Ryukyu group the Clausiliidce are present in abundance. 

 Except Stereophcedusa, none of the Japanese groups are represented, 

 the species I formerly referred to Hemiphcedusa being so far specialized 

 that thoy may more properly be segregated as separate groups. Luchu- 

 phcedusa and the Zaptychoid forms predominate. Some of them are 

 wonderfully specialized. Diceratoptyx, for instance, has almost lost 

 the lunella, which remains as a minute vestige only; the lower palatal 

 plica has been crowded upward, and its place taken by the dilated 

 subcolumellar lamella. Oligozaptyx and some Luchuphsedusas are 

 almost ec|ually modified in other directions. As a whole, the Clau- 

 siliidce are more specialized than those of either China or Japan, 

 and bear out the proposition I have elsewhere advanced, that insular 

 faunas age more rapidly than those of larger or continental areas. 



HeMIPH.EDUSOID PHYLUM. 

 Section MEGALOPH.EDUSA Bttg. 



Clausilia ducalis rex n. subsp. 



Larger and especially wider throughout than C. ducalis; superior 

 lamella contiguous to the spiral lamella, but not united with it; prin- 



* Seven papers haA'e appeared under the title "Additions to the Japanese 

 Land Snail Fauna," Parts II to VIII; one as "Catalogue of Clausiliidte of the 

 Japanese Empire," and one, "Land Mollusks of the Loo Choo Islands, Clau- 

 siliidse." All were published in these Proceedings, 1900 to 1903. 



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