Occasional Papers of the Museum of Zoology 5 



Habitat Study 



In order to make easier the comparison of the different 

 habitats and also to condense the paper, the Hsts of species 

 obtained from each habitat are combined into tables (Tables 

 I to V), instead of listing them at the end of each habitat. 

 Following the short descriptions of each habitat, any pecu- 

 liarities of distribution are mentioned ; otherwise it may be 

 taken that any particular species was quite equally distributed 

 throughout the habitat. 



For the purpose of making the descriptions of the abun- 

 dance of the different species as uniform as possible, the writer 

 has confined himself for some time to the following series of 

 terms : 



v.\ — very abundant F — frequent 



A-abundant ql— quite infrequent 



. -, I 1 ^ I — infrequent 



qA — fiu'.te abundant ^ . . 



vl — very infrequent 

 vC-very common qR^uite rare 



C — common |^ r^i-e 



qC — quite common vR — very rare 



Of course, such terms are at best very vague and indefinite 

 and do not take the place of a statistical study of abundance. 

 They probably do not exactly represent the comparative abun- 

 dance of very dissimilar habitats. However, as they are all 

 based on the observations of a single person, it would seem 

 that they are accurate enough for the comparison of more or 

 less similar habitats, especially those within a single series. 



While doing some statistical work on the distribution of 

 molluscs, the writer noticed that he had a tendency to uncon- 

 sciously over-emphasize the abundance of the larger forms and 

 to underestimate the comparative numbers of the smaller ones. 

 Fifteen or twenty specimens per square meter give one the 

 impression of considerable abundance in the uniones, more 



