My grateful thanks are due to him for ail this help, and, though the responsibility for the 

 présent work as now issued is solely mine, it owes a great deal to the earlier laborious work 

 of Monsieur Dautzenberg on the collection ; in fact, but for the condition in which I received 

 the collections and Monsieur Dautzenberg's help and notes, the report would hâve been 

 considerably delayed. 



The main part of the preliminary work in connection with the préparation of this report 

 was carried out in the laboratories of the Zoological Survey of India in the Indian Muséum, 

 Calcutta, but I soon realized that if the work was to be done properly, I must re-examine ail 

 the earlier material from the Indo-Pacific, which had formed the basis of the monographs of 

 the différent familles and gênera in the classical works of Reeve and Sowerby's "Conchologia 

 Iconica" ^), Sowerby's "Thésaurus Conchyliorum" ") and other rich collections which are preserved 

 in the British Muséum of Natural History, South Kensington, London. I, therefore, took the 

 earliest possible opportunity when I could get away from my officiai duties in Calcutta, and in 

 April, 1930, I went on leave to Europe. I worked during May and June on the "Siboga" 

 collections in the British Muséum, London, but later had to leave for America as I was deputed 

 by the Government of India to visit the United States of America for studying the Natural 

 History muséums and muséum administration in that country. I was away from London for 

 4 months, and it was not till the end of October, 1930, that I was able to résume my work in 

 London on the "Siboga" Pelecypods. The report was finished by the middle of February, 1931, 

 and the major part of the collection was returned to the Zoological Muséum, Amsterdam. The 

 types and other spécimens which are figured in this work were brought back to Calcutta, and 

 after the préparation of the photographs and illustrations hâve now been returned to Amsterdam. 



In the following pages I hâve included as complète synonymies of gênera as possible, 

 but in several cases, where detailed information on the subject is available in Dall's classical 

 work ^), I hâve not deemed it necessary to burden the report with the information already 

 contained in that work. A serious difficulty in référence to nomenclature and which was not 

 anticipated by Dall, has arisen from the fact that he was apparently not acquainted with 

 Children's work *). Children's conception of génotype or type as he called it, was far in 

 advance of even most later authors, and, even though in several cases his sélection of génotypes 

 was not a very judicious one, his désignation has to be accepted as the "type by original 

 désignation" (Article 30 of the International Rules of Zoological Nomenclature). This acceptance 

 unfortunately upsets several generic names which hâve been in gênerai use for a long time, 

 but since the main object of the International Rules is stability of zoological nomenclature, and 

 none of the names involved hâve already been placed on the officiai list of nomina conser- 

 va n d a , it is best that the correct names should be brought into use. I hâve carefully sifted 



i) Reeve, L. A. — Conchologia Iconica, I — XV (ex parte), London (1843 — -1865). 

 SowERBY, G. B. — Vols. XV (ex parte) —XX (London, 1865— 1878). 



2) SowEKKY, G. B. — Thésaurus Conchyliorum, I — V (1842 — 1887). Some of the monographs in this séries are the work of 

 S. Hanley. For dates of publication of the various parts see Woodward, B. B. — Catalogue of the books, etc. in the British Muséum 

 (Natural History), London, V, p. 1981 (191 5). 



3) Dall, W. H. — Contributions to the Tertiary Fauna of Florida. Trans. Wagner Free Inst. Sci. Philadelphia, III (1890— 1903). 



4) Children, J. g. — Lamarck's Gênera of Molluscs. This work was first published anonymously in Quart. Journ. Sci. Lit. Arts 

 as follows: — Vol. XIV, pp. 64—86 (1822); pp. 298—322, pis. III— VI (1823); Vol. XV, pp. 23—52, pis. II, III, and pp. 216—258, 

 pis. VII, VIII (1823) and pp. 241—264, pi. V, VI (1824). 



