034 ME. W. r. LANCHESTEB OK xiil [Dec. 3, 



2. On the Crustacea collected during the " Skeat" Expedi- 

 tion to the Malay Peninsula, together with a Note on 

 the Genus Act<eopsis. By W. P. Laxchestek, M.A., 

 King's College, Cambridge \ 



Part L— BEACHYUEA, STOMATOPODA, and MACEUEA. 



[Keceived November 15, IDOL] 



(Plates XXXIII. & XXXIV. 2 ) 



Owing to the number of species that are represented, through 

 the different groups, in the Crustacea collected by the " Skeat " 



Expedition, I have thought it best to divide the account of them 

 into two parts : the present paper dealing with the groups 

 mentioned above, the second paper to deal with the remaining 

 groups — namely, the Anomura, Arthrostraca, and Cirripedia. 



The present part deals systematically with 90 Bpecies, comprised 

 in 48 genera, so that the collection may be seen to he very fairly 

 representative; though the Oxyrhyncha, among the Brachyura, 

 are represented but poorly and the Leucosiid group or' the 

 Oxystomata not at all. Of these 90 Bpecies, moreover, 1 have 

 found it necessary to describe G as new — 2 among the Brachyura, 

 4 among the Macrura, — and to refer 2 forms among the Macrnra 

 to new varieties of already-known species. Further, I will note 

 that 50 of the species were obtained from localities on the east 

 coast of the Peninsula, 29 from the west coast, 5 from localities 

 on either coast (i. e., common to both), and of uncertain locality. 

 The small number of forms common to both coasts is not surprising ; 

 from two more closely situated localities, Singapore and Malacca, 

 I myself only succeeded in obtaining 12 common forms out of 

 120 species of crabs, and this I believe to be due very largely to 

 the differing nature of the sea-bottom, currents, &c, in different 

 parts of the same large area. Xot that I wish to give undue promi- 

 nence to this particular reason : the amount of time spent or the 

 facilities available in different localities are varying ; and, if I may 

 judge from my own experience, there is a disposition in the 

 collector not to overload his probably limited stock of bottles with 

 specimens he remembers to have already collected elsewhere. 

 These causes may easily bring it about that the number of 

 " common " forms is apparently so small. Notwithstanding this, 

 however, I am inclined to think that the smallness of the number 

 is not entirely apparent, but in part real; and what I would point 

 out is that the value of any collection from a given area would be 

 greatly enhanced were a species, or better a group of species, 

 dealt with distributionally, so that each specimen, or group of 

 specimens, collected might be accompanied by notes on the points 

 I have mentioned above (i. e., all details of habitat), in addition to 

 the note of simple locality. For,' besides the broad areas of 

 distribution that may be peculiar to a species, there are again 



1 Communicated by Dr. S. F. Harmer, F.Z.S. 

 a For explanation of the Plates, see p. 574. 



