156 Mil. GEOKFIIEV SMITH OX THE 



The Small Tasmanian Crayfish, Yar. tasmanicus. (PI. XV.) 

 (Eiichson, Archiv fiir jSTaturgeschichte, 12 Jahrg. p. 94.) 



This species (?), which occurs on Mount Wellington and 

 the southern and central ranges of Tasmania, reproduces on a 

 small scale almost all the characters of the large northern 

 and western A. franklinii, so that it may perhaps be considered 

 as only a small variety' of the large form. The following 

 chai'acters, which inay, however, be merely difl'erences due to 

 growth, may be referred to. There is a great reduction of the 

 tubercles upon the carapace and branchiostegites. The upper 

 margin of the carpopodite of the great chela has about six 

 serrations ; there is no pronounced enlargement of two tubercles 

 in the pincer. The inner border of the meropodite has about six 

 spines. The surface of the carpopodite is greatly pitted. The 

 spines on the walking-legs are reduced to very minute points. 



The colour is green. 



The length of fully adult specimens is never more than 

 5 inches. 



Localities. — Streams on Mount Wellington, Tasmania (1907). 

 A small specimen with the tubercles more prominent than 

 usxial, measm'ing 100 mm., from Traveller River, Lake St. Clair, 

 Tasmania (1893). Two small specimens from Zeehan, West 

 Coast of Tasmania. 



Beviarks on the above two species. — There are, in reality, no 

 distinctive characters, beyond those due to size, by which the 

 abo\ e two forms can be sejmrated. The fact, however, that the 

 small and large forms occupy different stations in different parts 

 of the island appears to preclude the possibility of the small 

 specimens being merely not fully-grown individuals of the large 

 form. A most curious fact is that I was unable to obtain 

 the young stages in growth of the large A. franMinii in the 

 rivers and streams, where the large individuals were fairly 

 common. The localities from which the large A. franklinii have been 

 obtained are invariably in the mouths of the streams near the 

 sea, and in these localities it is impossible, apparently, to obtain 

 small specimens. The small A. tasmanicus, on the other hand, is 

 always found inland in mountain-streams, often near their sources. 

 It is therefore within the bounds of possibility that the large 

 A .franklinii represents those individuals of the small A . tasmanicus 

 which haA^e succeeded in reaching the mouths of the rivei'S, but 

 that the young which they produce at these situations do not 

 arrive at maturity, owing to the presence of predatory fish, 

 e. g. Gadopsis marmoratiis. The species would then be entirely 

 recruited from the young of the small form, which breeds up in 

 the mountains. Exactly parallel facts are met with in the other 

 species of Astacopsis now to be described. A careful examination 

 of this question should be undertaken by a local naturalist. 



