310 



CELEBES CHAP. 



sented. Heyniplecta and Xesta are abundant and large, while the 



Rhysota of Borneo contain some huge sinis- 

 tral forms. Rliodina is a remarkable form 

 from Malacca, whose exact generic position 

 is not yet settled. Clausilia has a few species 

 on all the islands, the last occurring on 

 Ternate, and a single Papuina (Moluccas 

 and N. Guinea) occurs in Borneo. 



The Island of Celebes marks the be- 

 ginning of a distinct decrease in the Indo- 

 Malay element. The Naninidae lose 

 ground, in proportion to the Helicidae, 



T. onn 7 7 -^ Macrochlamys, for instance, beinor repre- 



FiG. 209. — Amphidromus ^^ ' ' , 



perversus L., Java. sentcd by Only one species, and Hemiplecta 

 by four. Other characteristic genera of 

 the Indian region dwindle, such as Amphidromus^ Clausilia, 

 the tubed operculates, and Cyclophoriis, while Sitala, Kaliella, 

 Grlessula, and Plectotropis disappear altogether. Compaiing 

 the total numbers of Naninidae and Helicidae from Sumatra to 

 New Guinea, we obtain this interesting result : — 



It will be noticed that the proportion of Naninidae to Helicidae, 

 which has been nearly 4 to 1 in Sumatra, falls to 3 to 1 in Java, 

 and rises again to 4 to 1 in Borneo (showing the essentially con- 

 tinental character of the island) ; in Celebes it further falls to 3 

 to 2, while in the Moluccas the scale turns and Helix has the 

 advantage by about 8 to 5, and in N. Guinea by more than 

 2 to 1. 



There is the same absence of marked features of individuality 

 in Celebes as in the islands dealt with above. Not a single 

 genus is peculiar. The nature of the sea bottom bet\veen Borneo 

 and Celebes, with its indications of a somewhat broad bridge over 

 an otherwise deep channel of separation, would seem to account 

 for and suggest the true explanation of the facts as they stand. 

 At the same time, there are indications of a certain amount of 

 contrast between N. and S. Celebes. The Indian element, which 

 constitutes the preponderating majority of the fauna, is common 

 to north and south alike. But the north part of the island, in 



