INTUODUCTIOX. 
Ten years have elapsed since the commencement of the present series of 
Monographs of the fossils which had been collected in the cretaceous deposits of 
South India during a geological survey of the Trichinopoly and South Arcot dis- 
tricts, The series was commenced in 18G2 hy Mr. H. T. JBlanford — under whose 
superintendence nearly all the fossils had been collected— by the description of 
the Belemnites and Nautili. At the end of 1862 I took charge of the con- 
tinuation of this series, and since then its publication has progressed without 
interruption, and with such little delay as the funds available for this object have 
permitted. To each of the classes of Mollusca, the Cefiialopola, Gastropoda, and 
Pelecypoda, or Bivalves, one separate volume has been devoted. The first volume 
was completed in 1865, the second in 1868, the third in 1871. The present fourth 
volume, which is devoted to the remaining portion of the invertehrata, and a few' 
vertehrata, commenced in 1872, and will, it is to he hoped, leave the printer’s 
hands by the end of April 1873. 
Beverting this order according to a more natiwal arrangement, w'e find that 
the different groups of animals are represented by the following numbers of species, 
most of which have been found sufficiently well preserved to he characterised 
and figured : — 
I. — Foraminifera, with a single well defined species, Orhitoides Fanjasi, 
Defr., and two doubtful ones. 
II. — Spongiozoa, with one species, Siplionia pyriformis, Goldf. 
III. — Corals, with 67 species. 
IV. — Fcjtinodermata (including Asterioiclea and Crinoidea) with 42 species. 
Y. — CiLioPODA (or Bryozoa, or Polyzoa) with 23 species. 
VI. — BRAcmopoDA, with 21 species. 
VII. — Pelecypoda, with 243 species. 
VIII. — Gastropoda, with 237 species. 
IX. — Cephalopoda,* with 146 species. 
* Comp, my additional remarks on this class in Records Geol. Surv. India, vol. I, 1868, pp. 32 to 37. 
