93 



OX A SPECIES OF THE LAND MOLLUSCAN GEXUS BYAKIA 

 FROM SIAM, 



By Lieut.-Colonel H. H. Godwin-Austen, F.R.S. 



EeadQth April, 1906. 

 PLATE X. 



I AM indebted to Captain Stanley Flower, who was in Siam in 1898, 

 for the land shell I now describe. He collected and preserved a good 

 many species in spirits which he was good enough to place in ray 

 hands. The genus Byalda., type Hugonis, Pfr., was described by me 

 in 1891 in a paper on a collection of land moUusca formed by the late 

 Mr. A. Everett in Borneo, a naturalist who discovered so many new 

 and beautiful species in that island.' 



In this genus I included certain species described by Professor 

 Semper,^ which he had placed in Ariophanta, a genus almost restricted 

 to Peninsular India, which has since been proved to be very distinct 

 and very distantly related to these Malayan forms. These species 

 were Rumphii, v. d. Busch, sinistral, from Java; nemorensis, Miiller, 

 dextral, from Celebes ; rareguttata, Mousson, dextral, from Adanara, 

 near Flores ; and striata, Gray, dextral, from -Singapur, this last 

 collected by Von Martens. It is the same shell as naninoides of 

 Benson, from the same locality. On a comparison of the shells in the 

 Natural History Museum a variety of this last species is, I find, the 

 subject of this paper, and was collected at Chantaboon, I show 

 further on its anatomical characters ; it well agrees with Professor 

 Semper's description and figures of this species on pi. iii, figs. 2\a--b, 

 with a few small specific differences. The interest lies in the generic 

 extension of range from Borneo and the Malay Archipelago and 

 peninsula very much more to the north up to the continental area. 

 Pfeiffer (Mon. Helic. Vivent., vol. i, p. 70) gives the island of Chusan 

 as a habitat of conicoides. This would be a remarkable distribution 

 for the genus, and I should like to see it really confirmed by examina- 

 tion of the animal. 



Dyakia striata (Gray), var. 



Sab. — Chantaboon (Capt. Stanley Flower). 



Specimen dissected. Diam. maj. 27, rain. 24-75 mm. ; alt. 13 mm. 



Animal. — Sole of foot (Fig. Ill) rather smooth, not divided, folded 

 down the centre by contraction in the spirit specimen. The extremity 

 of the foot very square (Fig. I), no lobe above the mucous gland 

 (Fig. II), which is an oval depression, and in life I imagine some- 

 what pit shaped [vide Wiegmann's drawing, pi. xxxvi, fig. 13, of 

 B. Hugonis ?). 



Sides of foot rather smooth, the peripodial grooves distinct, with 

 a broad fringed margin below them (Fig. I). The dorsal lobes 



' Proc. Zool. Soc, 1891, ])p. 22-47. 

 2 Reiseu im Archipel der Pliilippiuen. 



