X. ON THE GENERIC POSITION OF HELIX 

 DI ST I N CT A , PFR., OF SIAM. 



By Li.-Colonel H. H. God win- Austen, F.R.S. 



I have to thank Dr. N, Annandale for sending me a small 

 but interesting collection of land mollusca from Siam, a dona- 

 tion to the Indian Museum, Calcutta, got together by Mr. C. 

 Boden Kloss (5-V17). One interesting species, which I now 

 describe, he obtained at Lat Bua Kao, 30 miles west of Korat — a 

 locality described by Mr. Kloss in "The Ibis" 1918, p. 78.. as 

 "just within the eastern foot of the hills which separate the 

 slightly elevated, shallow basin of eastern Siam from the central 

 Siam plain and the Menam river-system." There are six or 

 more fine specimens preserved in spirit, the largest measuring 

 68 mm. in major diameter. It affords me the opportunity of 

 comparing the animal with other large species from that part 

 of the world, such as Hemiplecta humphreysiana and ftoweri, with 

 which I have dealt. The latter is fully described and figured 

 in Proceedings Malacological Society, Vol. IV, March, 1900. Com- 

 parison with this Siam shell should therefore be of much interest. 

 In this paper I also described Hemiplecta neptuna, Pfr., received 

 from ray old friend and fellow-worker the late Dr. W. T, Blanford, 

 also from Siam and sent to him by Mr. Daly. I alluded also to 

 Helix distincta^ Pfr,. and pointed out there was much to be 

 cleared up. 



Helix distincia, described by Pfeiffer in 1850, is recorded 

 in 1853 by him in Mon. Hclic. Vivent. Vol. HI, p. 81, as from the 

 Moluccas. We next have it recorded from Siam by Von Martens 

 in his Preus. Exped. n. Ost-Asien, 1867, P- 69, and placed in. 

 Nanina of Gray. The external characters of the animal are 

 only referred to, and there is not a doubt he had before him tnis 

 fine large Siam species which is the subject of this paper. The 

 drawing of the animal (plate 6, fig. 8) shows clearly it has 

 right and left dorsal lobes but no shell lobes, and the same is 

 seen in the drawing of N. siamensis, Pfr., fig. 6. 



Later in 1900, quoting from my paper on the anatomy of 

 Hemiplecta floiueri, E. A. Smith, I wrote '' Professor Semper in his 

 Reisen im Archipel der Philippinen Bd. Ill, p. 62, pi. vi, fig. 27, 

 under Xesta distincta, mentions having obtained two shells from 

 Zamboanga, in Mindanao. He, however, described the animal, 

 and figured the jaw and radula of a young specimen from Saigon, 

 Cochin China, which is over 500 miles from Siam. The jaw 

 has no central projection; the central tooth and admedians are tri- 

 cuspid, the laterals bicuspid, with 160 to 180 teeth on each 



