20 BARBOUR: ZOOGEOGRAPHY. 



map published in the report of the Valdivia expedition are mostly in places 

 where they are of very little interest to us. Southeast of Engano there are two 

 soundings, one of 1,104, the other of 732 fms.; to the northwest a single sounding 

 of 637 fms. is given; and northward in the Indian Ocean a depth of 2,744 fms. 

 occurs. In a direct line between Engano and the mainland of Sumatra, and 

 between Engano and Mega, no soundings have been made. 



We know of the herpetology of the island through the collection of Elio 

 Modigliani, which were reported upon in 1892 by Vinciguerra (Ann. Mus. civ. 

 Gen., ser. 2, 12, p. 517-526). 



A single fresh-water turtle, Cyclemys ambonensis (Daudin), is known. This 

 is interesting, as in the other islands the single known fresh-water turtle is 

 Cyclemys dhor (Gray). Assuming that the identifications are correct, and that 

 there is only a single species on each island, this may prove to be an ultimate 

 clue to a different origin for the fauna of Engano from those of the other islands. 



Of the lizards, Gymnodadylus marinoralus (Dum. & Bibr.) occurs in Sumatra 

 and Engano, as well as elsewhere, though it does not occur on either Nias or 

 Sipora. Lepidodactylus ceylonensis Blgr. has been found in Ceylon, Borneo, Java, 

 and Engafio. Draco rnodiglianii Vinciguerra is peculiar to the island. Siaphos 

 relictum (Vinciguerra) is known only from Sipora and Engano. Altogether 

 about nine species of lizards have been reported, less than from the other islands; 

 but whether this is because it has been less carefully studied, is a question which 

 only time will answer. 



Among the snakes, Elaphe enganensis (Vinciguerra) is peculiar to the island, 

 and only two other species have been recorded — one the free-swimming Hurria 

 rhynchops (Schneider), the other the tree-snake, Psammodynasles pulverulentus 

 (Boie). 



I find in van Kampen's records but two amphibians, Rayia macrodon Dum. 

 & Bibr., and R. nicobariensis (Stoliczka). 



From the above it is evident that the facies of this fauna is quite distinct 

 from that of either Nias or Sipora. Whether this is due to a longer isolation, 

 or to our incomplete knowledge, it is impossible to say; and whether future 

 soundings will develop closer relationship with the southern Mentawei Islands 

 or with Sumatra itself, is a point of great interest. There is, of course, a possi- 

 bility that this island never has been connected with the mainland, though 

 the fauna, as we know it now, contains several species which it would be very 

 strange to find on an oceanic island. The mere fact of the existence of a deep 

 channel between Engano and Sumatra, would not, however, necessarily pre- 



