CONCHOLOGY. 159 



LAND SHELLS. 



The following observations on the land shells of Burma, their relationship ami 

 distribution, are from the pen of Mr. W. T. Blanford, and are so pertinent that I 

 make no apology for extracting them verbatim from the Li. 15. Gazetteer, for which 

 work they were written : — 



"Taking the land shells first, it should be recollected that they belong to two 

 different classes of MoUusca, but to two classes very much more closely allied to 

 each other than to any of the other classes into which the MoUusca are divided. 

 These classes arc: (1st) The operculated land shells, which are fre(iuently arranged 

 apart from the ordinary univalve shells of the seas or rivers, _ .such as whelks, 

 periwinkles, and Fdluili/iida, on account of having a breathing chamber not 

 furnished with certain appendages known as gills; and (2nd) the Pulmonata, or 

 true snails, without opercula. By those naturalists who attach great importance 

 to the modifications of the breathing organ, the operculated land shells are some- 

 times classed as a peculiar order or sub-order called Xeurobmnchiata, and sometirae.s 

 united with the true Palmonnta. The latter course is certainly a mistake, for the 

 two groups differ in almost every detail of their organization, and even the form 

 of the breathing chamber is quite distinct; and as the only difference of any 

 importance between the so-called Xeurohranchiata and the ordinary Gasteropoda or 

 Prosohranchiata consists in the adaptation of the breathing sac in accordance with 

 the medium in which each form lives, (as there is in some families, as LittorinidcB 

 and Rissoid(C, a gradation between pure air breathers and pure water breathers, and 

 as an instance is even known in the estuariue genus Cerithidea inhabiting brackish 

 creeks and salt swamps of two closely allied species, one possessed of gills and the 

 other quite destitute of thon,) it is plain that the distinction is adaptative and of no 

 structural importance as evidence of relation. 



Both of the two grou])S of land shells, the operculated and the non-operculatcd, 

 or the air-breathing Prosohranchiale Gasteropoda and the Pulmonata, are represented 

 by numerous species in Burma. The former, indeed, are very much more common, 

 and represented by many more forms in Burma than in the Peninsula of India 

 generally, with the exception, perhaps, of the hills along the Malabar coast. 

 Their forms, too, are, on the whole, more remarkable and varied, and some of them 

 are exquisitely coloured or sculptured. Many are minute, but the largest are of 

 considerable size, some forms of Ci/dophorus being upwards of two and a half inches 

 in diameter. The non-operculate shells also vary in size, but minute forms are 

 rather less numerous. 



A list of the known Burmese land shells is given in the following pages. 

 Figures of almost all of these will be found in the ' Conchologia Indioa ' of Hanley 

 and Theobald, but the descriptions are scattered through many different works, and 

 can only be found united in Pfeiffer's ' Monograpliia Heliceorum ' and ' Mono- 

 graphia Pncumonopomorum,' neither of which is illustrated. The former contains 

 the non-operculate forms, the latter those possessed of opercula. 



The following are the genera occurring. Those in the first family noticed — the 

 Jtissoida — are of minor importance, '^he Rissoids are princij^ally small marine 

 estuarinc and freshwater shells, and it is uncertain whether Acmrlla is justly referred 

 to them. Truncatella is scarcely a laud shell, being confined to the sea-shore. 

 Acmclla hijalina is a very minute hyaline, smooth, conoidal form of doubtful affinities, 

 and only found liitherto on limestone hills near Maulmain. The family Poniatiasidm 

 contains only the genus Pvmatias, which is abundant in Southern Europe, and is 

 represented by isolated species in the Eastern Himalayas, the ranges south of the 

 Assam valley, and the Arakan Hills, whore one form is found. The shells are 

 turrited in texture and finely ribbed. The CyclophoriilcB ( Cijclotidie or Ci/chtacea of 

 many writers) comprise the great bulk of the operculated land shells of Burma and 

 of the neighbouring countries. They are divided into three well-marked families. 

 1. The Cyclvphorina, discoid or conical shells frequently richly coloured or with a 

 rough epidermis. 2. The Diplommatinida, discoid, conical, or ovate, all of one colour 



