Herriott. — Occurrence and Habits of Lepidurus viridis. 291 



from the same pool, and are probably only different stages in the develop- 

 ment, due to the age of the individual. This is borne out in the study on 

 which this paper is based. 



Lubbock (1863, p. 206) notes in the case of a character Baird used — 

 namely, the extent to which the body of the animal is covered by the 

 carapace — that his specimens taken from gravel-pools in the north of 

 France showed a great amount of variation in this respect. In some in- 

 stances the carapace left seven posterior segments uncovered, in others it 

 covered part of the caudal lamella. He notes that the shape even of the 

 caudal lamella varied. 



. G. M. Thomson (1879, p. 261), at the very time of describing his two 

 new species, expresses as his opinion that these may be only varieties of 

 a widespread species, and would " be inclined to include under one species 

 L. productus Bosc, from Europe, L. viridis Baird, from Tasmania, L. angasii 

 Baird, from South Australia, and perhaps even L. glacialis Kroyer, from 

 North America." 



Spencer and Hall (1896, p. 233), after examining a large number of 

 specimens of Lepidurus, come to the same conclusion, that a comparative 

 study of all the species known from different parts of the world " would 

 result in materially reducing the number of species." 



The specific characters used by different writers appear to be — (1) Size 

 of animal ; (2) extent to which carapace covers body ; (3) shape and thick- 

 ness of carapace ; (4) colour ; (5) shape of caudal lamella ; (6) length of 

 caudal setae or cercopoda. Most of these have been mentioned, and have 

 been shown not to be constant characters, but in this paper I make no 

 attempt to discuss the specific distinctions of the specimens examined. 



Bibliography. 



Baird, W.. 1850. Description of Several New Species of Entomostraca, 



Proc. Zool. Soc., 1850, p. 254. 

 1866. Description of Two New Species of Phyllopodous Crustaceans, 



Proc. Zool. Soc, 1866, p. 122. 

 Bernard, H. M., 1892. The Apodidae. 

 Calman, W. T.. 1909. Ray Lankester's Treatise on Zoology, pt. vii, 



Appendiculata ; Third Fascicle — Crustacea. 

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Soc., vol. 24, pp. 205-9. 

 Packard, A. S., 1882. Monograph of the Phyllopod Crustacea of North 



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Species, Trans. N.Z. Inst., vol. 11, pp. 260-1. 

 Weldon, W. F. R., 1909. Cambridge Natural History, Crustacea, chap. ii. 



U.)" 



