1900.] FROM SINGAPORE AND MALACCA. 721 



should like to say that they have been chosen, in nearly every 

 instance, for one of two reasons, apart from those of synonymy : 

 1st, that the reference given contains a good description, or figure, 

 or useful additional remarks ; 2nd, that the reference points to the 

 occurrence of the species in India or Australia, with the neigh- 

 bouring seas, or that its existence has been previously noted at 

 Singapore or Malacca. 



Before proceeding to the account of the species, I should like 

 to take this opportunity of expressing my personal thanks to the 

 following gentlemen, who received us most kindly, and gave us 

 valuable facilities in the pursuit of our object : Sir Alexander 

 Swettenham, C.B., at the time of our visit Acting Governor at 

 Singapore ; Dr. R. Hanitscb, Curator of the Baffles Museum, 

 who gave us the free use of a room in the Museum, and also 

 useful advice as to collecting-grounds ; Mr. H. N. Ridley, Curator 

 of the Botanical Gardens, to whom I am particularly indebted 

 for the . new variety of Potamon tridentatum described below, 

 and for the brief account of its burrowing habits (which I repro- 

 duce from memory) ; and also to the Hon. W. Egertou, Resident 

 Councillor at Malacca. At home, I have to thank Prof. Jeffrey 

 Bell for the very kind way in which he has placed a room at my 

 disposal in the Natural History Museum, and for kindly com- 

 municating this paper to the Society ; and Mr. G. A. Boulenger, 

 for very useful advice given in connection with this paper. 



Note. — In the measurements given, the first figures invariably 

 represent the breadth: e.g. 10x7=breadth 10, length 7. All 

 measurements in millimetres. 



I. Genus Achceus Leach. 



1. Ach^us lacertosus Stimpson. 



Achceus lacertosus, Stimpson, Proc. Acad. Nat. Sci. Philad. p. 218 

 (1857). 



Achceus breviceps, Has well, Proc. Linn. Soc. N. S. W. vol. iv. 

 p. 433 (1879). 



Achceus lacertosus, Miers, Alert ' Crust, p. 188 (1884 ); Henderson, 

 Trans, Liun. Soc, Zool. vol. v. p. 341 (1893). 



Hah. Singapore ; 6 fms. One male. 



Dim. 3-5x4. 



2. Achjeus lorina Ad. & White. 



Inachus lorina, Ad. & AVhite, ' Samarang ' Crust, p. 3, pi. ii. f. 2 

 (1848). 



Hah. Singapore ; 6 fms. Sandy mud. One male. 

 Dim. 5-75 x 7*5. 



II. Genus Camposcia Latr. 



3. Camposcia retusa Latr. 



Camposcia retusa, Latr. Regue Animal, 2 C ed. t. iv. p. GO (1829); 



