284 Transactions. 



Art. XIX. — Notes on the Occurrence and Habits of the Fresh- water 

 Crustacean Lepidurus viridis Baird. 



By Miss E. M. Herriott, M.A. 



Communicated by Dr. Charles Chilton, C.M.Z.S. 



[Read before the Philosophical Institute of Canterbury, 6th December, 1916 ; received by 

 Editors, 30th December, 1916 ; issued separately, 16th August, 1917.] 



Introduction. 



In some of our rain-water pools formed in gravel or shingle pits during 

 the spring rains the interesting crustacean Lepidurus viridis occasionally 

 makes a sudden appearance. For a few weeks it flourishes and may be 

 collected in large numbers, then as the hotter months of summer come 

 the pool dries up and the animal disappears, to reappear perhaps in a similar 

 way at the same time of the following year, or, it may be, to be seen no 

 more in that locality for several years. In this paper are recorded observa- 

 tions made recently on collections of living specimens kept for two or three 

 weeks in the Biological Laboratory at Canterbury College, and the informa- 

 tion available from previously published records is collected. These records 

 are apparently very scanty. 



Historical. 



Lepidurus viridis belongs to a group of the crustaceans commonly 

 known as the Phyllopoda, and is interesting not only on account of its 

 size and structure, but also because Bernard (1892) attempts to make 

 of the group a connecting-link between the Annelida and the higher types 

 of Crustacea. The Phyllopoda (so called because the numerous append- 

 ages are membranous and foliaceous, thus serving the double purpose of 

 limbs and respiratory organs) is further subdivided into families, to the 

 lowest of which — namely, to the Apodidae — this genus belongs. This is 

 a small family consisting of only two genera, Apus and Lepidurus. These 

 agree in having a long segmented body, from fin. to 2| in. or 3 in. long, 

 partly covered with an oval shield-like dorsal carapace, and bearing at the 

 posterior end of the body two jointed appendages, or " cercopoda," which 

 vary in length. The chief difference between the two genera is the presence 

 in Lepidurus of a long produced telson and a larger carapace (Packard, 

 1882, p. 316). This large plate or caudal lamella of the telson is shaped 

 " like a beaver's tail, and must give it an advantage over Apus in extri- 

 cating itself from muddy places " (Packard, 1882, p. 380). 



The species Lepidurus viridis was described and figured by W. Baird 

 (1850, p. 254). His description was based on the examination of one 

 animal from Tasmania, 2 in. long and 1 in. broad, " of a fine green colour." 



In 1866 two more specimens were sent to Baird from "rain-pools 

 on the Gawler Plains, north of Adelaide, South Australia " (1866, p. 122). 

 This animal was just 1 in. in length ; the caudal setae were rather more 

 than half the length of the body, and in spirit the carapace was a pale 

 horny colour. Baird therefore made of it a new species, Lepidurus angasii. 



