[CEYLON PEARL OYSTER FISHERIES 1905 SUPPLEMENTARY REPORTS, No. XXIII.] 



REPORT 



ON THE 



ISOPODA 



COLLECTED BY 



Professor HEEDMAN, at CEYLON, in 1902. 



BY 



The Rev. THOMAS R. R. STEBBING, M.A., F.R.S., Sec. L.S., F.Z.S., 



FELLOW OF KING'S COLLEGE, LONDON. 



[With TWELVE PLATES.] 



The interest of the present collection is not to be measured by the number of species 

 or the number of specimens, still less by the size of the animals. The species are not 

 numerous, the examples in many cases are few, and of some the dimensions have 

 proved to be afflictingly small. On the other hand, there is no want of variety, since 

 the thirty-four species more or less definitely discriminated are spread over five very 

 distinct tribes and divided among sixteen families. There is no want of novelty, since 

 two of the families, three of the genera, and fourteen of the species are now added to 

 science on what appear to be satisfactory grounds. Certainly the family Amesopodid^e, 

 founded on some small creatures allied to Idotea, must be thought well worthy of 

 notice. 



The only family illustrated by a rather large supply of specimens is that of the 

 Sphferomidse. But the supply has not thrown much convincing illumination on the 

 difficulties of this group, which have of late years arrested the attention of several 

 writers. Any person of impatient temper who has ever attempted, when pressed for 

 time, to disentangle with unskilful fingers a knotted skein of string, may understand 

 the plight of a busy naturalist who has Sphaeromidre to classify. There is always the 

 chance in regard to this family that, after struggling with the complexities of the 

 situation, one may have done more harm than good, by adding to the confusion instead 

 of lessening it. It is, indeed, a general disadvantage attending the description of a 

 local fauna, or of a special collection, that it may involve the fragmentary treatment 

 of problems which can only properly be solved by a monographic survey. 



The tribal division of the Isopoda is here accepted from the invaluable ' Crustacea 

 of Norway,' by Professor G. O. Sars. 



B 



