362 [Mar. 6, 



joints of the first and second pairs of legs are tolerably perfect ; of 

 the third and fourth pairs the basal joints alone remain, and the 

 fifth pair is lost. The whole of the abdomen, with the exception of 

 the third segment, is very perfect ; it is abruptly bent forward upon 

 itself, the terminal joint resting beneath the thorax, between the third 

 and fourth pairs of legs (j^ff. a). The rostrum also is very perfect, 

 broken off from the carapace, and lying vertically between the an- 

 terior legs (Jig. c). It is prolonged into a grooved triangular tooth, 

 and there is a small prominent tubercle on each side, at a short dis- 

 tance from it. The raised lines, circumscribing the rostral tooth, 

 are continued backwards to some distance, as is also its deep me- 

 dian groove. A second raised line is continued backwards from 

 the small denticle, or tubercle, on each side. 



The similarity between this species, as far as the state of the 

 fossil will allow of the comparison, and the recent one, is so great, 

 that there is some difficulty in fixing upon valid distinguishing 

 characters. It differs, however, in the proportion of the epimeral 

 or lateral portions of the abdominal segments, which are somewhat 

 less developed in the fossil than in the recent species, and in the 

 form of its terminal segment, or middle lobe of the tail, the length 

 of which is to its breadth in the fossil as 8 to 6, and in the recent 

 species as 11 to 6. The sides of the carapace are, in the former, 

 somewhat more uniformly covered with minute raised points, 

 which, in both species, render the surface bistinctly scabrous. 



This specimen derives additional interest from its being the 

 only fossil Crustacea which has yet been found in New Holland. 



March 6, 1844. 



The following communications were read : — 



1. On Two Fossil Species of Creseis (?) collected hy Professor 

 Sedgwick. By E. Forbes, Esq., F.E. S., F.L. S., Professor of 

 Botany in King's College, London. 



Creseis is a genus of Pteropodous Mollusca established by M. 

 Sander Rang to include several species of simple, more or less aci- 

 cular shells. Their surface is smooth or transversely striated, 

 rounded, and sometimes presenting a longitudinal groove. The 

 animal resembles that of Hyalcea, but is not furnished with the 

 two caudiform lateral appendages with which the Hyalcea is pro- 

 vided. All the species are small, none being more than an inch in 

 length. They are oceanic animals, free swimmers, and their re- 

 mains are found in abundance in the fine mud of great depths. 



