330 DR. O. F. VON MOELLENDORFF ON [JunC 2, 



The Secretary exhibited on behalfof Mr. F. E. Blaauw, C.M.Z.S., 

 specimens of some Long-tailed Tits shot by him last year in Holland 

 and belonging to the museum of the Royal Zooh)glcal Society 

 " Natura Artis Magistra," They had been sent to this country for 

 the purpose of ascertaining whether they belonged to the British 

 form Acredula rosea or the white-headed Continental form A. cau- 

 data (see Dresser's 'Birds of Europe,' vol. iii. pp. 63-67). There 

 could be no doubt that these birds belonged rather to the British 

 form with striped head ; but Mr. Blaauw'stated that the white-headed 

 form was also met with in Holland, and that he had occasionally 

 observed examples of the two forms paired together. 



Mr, Frank Finn, B.A., exhibited a male hybrid between the 

 Chilian Pintail {Bafila sjnnicauda) c? and Summer Duck (^,v 

 sponsa) § , bred in the Gardens, and pointed out that it differed 

 from both parents, though it was to a certain extent intermediate. 



The following papers were read : — 



1. On the Land and Freshwater Shells of Perak. 

 By O. F. von Moellendorff, Ph.D. 



[Keeeived April 15, 1891.] 



(Plate XXX.) 



Since the publication of my paper on the Land-Shells of Perak 

 (Journ. As. Soc. Beng. Iv. pt. ii. no. 4, 1886), Dr. R. Hungerfoid 

 has been kind enough to supply me with some more materials from 

 that hitherto very imperfectly known region. Mr. J. de Morgan, 

 who collected in Perak in 1884, published descriptions of some new 

 species in • Le Naturaliste ' (vii. 1885, no. 9, pp. 68-70), and gave a 

 more extensive memoir on the conchological fauna of the Malacca 

 peninsula in the Bulletin Soc. Zool. de France (x., 1885), with figures 

 of his novelties. This latter work I did not know of wlien I wrote 

 the above-mentioned paper, and the study of it now enables me to 

 rectify some of my former classifications, and at the same time to 

 correct a number of errors contained in de Morgan's work. I think 

 it therefore advisable to give now a revised catalogue of all the 

 Land and Freshwater Shells at present known from Perak, with 

 descriptions of some further new species. 



Fam. Streptaxid^. 



1. Streptaxis plussensis, de Morgan. 



Streptaxis plussensis, de Morgan, Le Nat. 1885, p. 68 ; Bull. 

 Soc. Zool. Fr. x. 1885, p. 23, t. i. fig. 1. 



Mt. Tchehel, Pluss valley {de Morgan). 



A good new species, somewhat related to (S*. lemyrei, Morel., from 

 Cambodia. 



Dr. Hungerford obtained at Bukit Pondong a few specimens o 



