OF MEKGUI AND ITS ARCHIPELAGO. 



219 



Moluccas, and even to Polynesia, many of which were well known 

 to the early conchologists of the ante-Linnean period ; and of these 

 we find a large number also on the Tenasserim coast. Others 

 appear to be confined to that part of the Indian Ocean which 

 includes the Andaman s,' Nicobars, and the Tenasserim coast ; 

 some of them were known to the older Danish conchologists 

 (Chemnitz, Spengler ; the Kicobars being a Danish possession at 

 the close of the last century), but are still rare in collections, e. g. 

 Pholas quadrizonalis. 



The statements concerning the occurrence at low-water, on 

 mud-flats, on mangrove-trunks, &c, yield many hints concerning 

 the relations of the shapes and colours of the shells to their 

 peculiar habitats, which will be very acceptable to most concho- 

 logists. It is also very remarkable that some species, unani- 

 mously considered as marine, e. g. Nerita lineata and Columbella 

 Duclosiana, have been found associated in brackish water with 

 others generally regarded as freshwater shells, e. g. Neritina 

 crepidularia ; and that some species of JVeritma, such as N.nala- 

 ne?isis, have been found alike in fresh and in brackish waters. 

 This proves that the distinction between freshwater and marine 

 species is in some families not so well defined as has been generally 

 surmised. 



DESCRIPTION OF THE PLATES. 

 Plate XIV. 



Figs. 1-6. Cyclophorus aurantiacus. 1, 2, var. a, typicus; 3, 4, var. b, per- 

 nobilis ; 5, 6, subvar. bb (paulo minor). 



Plate XV. 



Figs. 1-6. Cyclophorus aurantiacus. 1, 2, var. c, Nevilli; 3, 4, var. d, Beevei: 



5, 6, var. e, Andersoni. 

 Figs. 7, 8. Cyclophorus expansus. 

 Fig. 9. Cyclophorus zebrinus, var. c, ambiguus. 



Plate XVI. 



Fig. 1, a,b, c. Kassa Ther sites, var. acypha. 



Fig. 2. a-f. Littorina rubropicta, n. sp. 



Fig. 3, a-e. Isanda pulchella. 



Fig. 4, a-d. Mytilus (Aulacoma) curvatus. 



Fig. 5, a, b, c. Mytilus (? Septifer) Andersoni, n. sp. 



Fig. 6, a, b. Mesodesma cequilaterum. 



Fig. 7, a, b. Lutraria (Merope) nicobarica. 



LI>~N. JOUEN. — ZOOLOGY, VOL. XXI. 



18 



