LAND AND FRESHWATER MOLLUSCS OF PONDICHERRY

The state of Pondicherry, having an area of 492 sq. km., is spread in four parts viz., Pondicherry, Karaikal, Mahe and Yanam. The former two are situated on the coast of Bay of Bengal, south of Chennai (Madras) between Tranquebar and Nagapattinam (in the districts of South Arcot and Tanjavur) in the state of Tamil Nadu. Mahe is situated on the west coast of India between Tellicherry and Badagara in the state of Kerala; whereas 'Yanam', a land locked area is situated south of Kakinada in east Godavari district in the state of Andhra Pradesh. Before merger into Indian Republic, these were under French territory.


INTRODUCTION
The state of Pondicherry, having an area of 492 sq. km., is spread in four parts viz., Pondicherry, Karaikal, Mahe and Yanam. The former two are situated on the coast of Bay of Bengal, south of Chennai (Madras) between Tranquebar and Nagapattinam (in the districts of South Arcot and Tanjavur) in the state of Tamil Nadu. Mahe is situated on the west coast of India between Tellicherry and Badagara in the state of Kerala; whereas 'Yanam', a land locked area is situated south of Kakinada in east Godavari district in the state of Andhra Pradesh. Before merger into Indian Republic, these were under French territory.
Our knowledge on the molluscan fauna of Pondicherry state is based on the earlier works by Blanford and Godwin-Austen (1908), Gude (1914Gude ( , 1921, Preston (1915) in 'Fauna of British India, Mollusca series and also by Satyamurti (1960). Though marine molluscs of Pondicherry are well known, our knowledge on land and freshwater molluscs are very limited. The present studies were carried on the basis of recent collectior.s made by Southern Regional Station, Zoological Survey of India, Chennai and also the literature records.
There are three species of molluscs described from the state of Pondicherry, of which two are freshwater, viz., Paludolnus acutus Reeve, 1852 (=P. tanschauricus Gmelin) and Corbicula striatella Area-wise, the state of Pondicherry is one of the smallest states in India, hence the number of species recorded is also very small while compared to other states. Forest cover, plays an essential role in distribution of land mol1uscs. Since forest coverage is less in the state of Pondicherry that could be a reason for less number of species occurring there. Renlarks : Shell of this species is variable in its shape of the spire and colour. It is distinguished from the other common species P. globosa in being less inflated and having a narrow aperture.
The whorls are rather horizontally flattened above at the sutures. Elsewhere: Sri Lanka. Rec. zoof. Surv. India Height of the aperture 3.0-3.10 Rel11arks : Shell globosely conical, perforate, with strong spiral ridges five of which are more strong with a few finer ones in between.
Family UNIONIDAE Genus ullnellidells Simpson, 1900 Shell elongately elliptical, smooth without strong sculpture, anterior end narrow, posterior broad, often with a posterior ridge, umbo prominently swollen and with curved radiating ridges, periostracum shining, brown to dark brown, left valve with two elongated cardinals and two laterals, right with two lamellar cardinals and one lateral. Elsewhere: Sri Lanka.
Height of the aperture 13.6 Remarks : Shell rhomboidal, thick and broad, unbones prominent, dorsal margin obliquely truncate at posterior end which is obtusely angled, anterior end rounded, biangulate posterior ridge well developed, left valve with two ragged cardinals. This species is for the first time recorded from Pondicherry.

Lamellidens corrianus
This species is for the first time recorded from Pondicherry.

SUMMARY AND DISCUSSION
Based on the present studies a total of 20 species under 15 genera and 13 families of both land and freshwater molluscs are recorded from the state of Pondicherry. Out of these, 13 species are from freshwater and only 7 species are from land. Six species viz., Gabbia stanothyroides, Thiara tuberculata, Parraysia favidens, Lanlillidens consobrinus, L. Corrianus and Cryptozona bistrialis are reported for the first time from Pondicherry. The last mentioned species is a land mollusc. The material available for studies are from Pondicherry and Karaikal only. No material was available for the study from other parts of the state, 'Mahe' on west coast and 'Yanam' near Kakinada on the east coast.
Freshwater gastropods such as Mysorella costigera, Gabbia stenothyroides and Paludomus tanschauricus are restricted to Peninsular India. Rest of the species have all India range of distribution.
Pondicherry forms a part of Peninsular India which constitutes a very distinct zoo-geographical region in India. Referred as 'India Vera' (Mani, 1974) this region contains some of the relics of the Gondwana fauna. Approximately, over 200 species of land and freshwater molluscs under 70 genera are known from the plains of Peninsular India. But the number of species recorded from Pondicherry is too small and may not represent the actual figure of species occurring in that area.