87 
27. Donax Keyur, A. Adams. D. testa trigonali, inequilate- 
rali, latere antico abrupte truncato, epidermide fusca, tenui 
obtecta, oblique valde costata, costis equalibus, interstitis 
concinne cancellatis ; margine ventrali denticulato, arcuato, 
postice subsinuato ; intus, ad laterum anticum, macula oblonga, 
violacea ornata. 
Hab. Hippopotamus Point, Quilimane River, East Africa (Gilbert 
Key, Esq., R.N.). 
A very pretty and curious species, characterized by the strongly- 
marked oblique ribs with the interstices cancellated, and with a violet 
spot in the interior of the valves. 
March 14, 1854. 
Dr. Gray, Vice-President, in the Chair. 
The following papers were read :— 
1. OBSERVATIONS ON THE GENUS PALUDOMUS OF SWAINSON, 
WITH DESCRIPTIONS OF SEVERAL New SPECIES, AND THE 
DescrirpTion oF A New Sprecires or Ancutotus. By 
Epear L. Layarp, F.Z.S., C.M.E.S. erc. ere. 
A cursory survey of the genus Paludomus, which Swainson many 
years ago separated from Melania, at once satisfied me that several 
genera or subgenera, differing in structure and habits, were united 
together under one name by Mr. Reeve, in his monograph on the 
genus in the ‘ Conchologia Iconica,’ where he describes the charac- 
ters of the genus as follows :—‘* Animal fluviatile, with a horny sub- 
triangularly-ovate concentrically-striated operculum.” 
_ Had Mr. Reeve been furnished with the operculum and a correct 
account of the habits of each species, he never would have left the 
genus as it now stands. I was not aware that Dr. Gray had sepa- 
rated one division from it, until so informed by him when I intro- 
duced the subject to the notice of the Zoological Society on a former 
evening ; and I rejoice to find that my observations on the Mollusca 
in their natural state confirm the views to which that learned zoolo- 
gist has arrived, from the structure of the opercula. 
This induced me carefully to examine the whole group; and the 
ample collection of Mr. Cuming, ever open to the investigator, my 
own cabinet, particularly rich in this family, and my memoranda 
taken in Ceylon, have furnished the results here presented to the 
Society. 
I propose to separate the genus into four divisions, founded upon 
the structure of the operculum. 
The first I shall designate Paturomus, as, with the addition of 
the position of the nucleus in the operculum, the characters, as given 
