STDDIES IN ADSTRALTAN CRUSTACEA McCDLT.OCH. 237 



Notes on Variation in Astacopsis serratds, Sliaw. 



(Plate xHii.) 



The common Crayfish or Fresli -water Lobster of Eastern 

 and Soutliern New South Wales and Victoria undergoes con- 

 siderable alteration in its armature and ornamentation durinef 

 transition from the younCT to the adult stages. It is also sub- 

 ject to considei-able variation at all ages, but particularly 

 when about 100mm. long, at which size it begins to develop the 

 large tubercles and spines which are chai'acteristic of full- 

 grown specimens. 



The species is represented in the AiTstralian Museum collec- 

 tion by a fine series of over seventy specimens fj'om vai'ious 

 parts of New South Wales, which are well graduated in size. 

 The smallest specimens, -iSmni. long (measured from the end 

 of the rostrum to that of the telson), have the carapace nearly 

 smooth, but it gradually becomes granular as they increase in 

 size until a length of tibout 95mni. is attained, when lai'ger 

 tubercles and spines begin to make their ap[)earance. Twenty 

 full-grown examples, 160-260mm. long, are the typical A. 

 serratus as figured by Shaw^, wjth large spines or tubercles on 

 the posterior half of the carapace, and numerous stout spines 

 on the abdomen. 



Some examples of intermediate size, measuring up to 

 132mm. in length, have not developed the armature character- 

 istic of the adult stages, but have the hinder poition of the 

 carapace granular and the abdomen without spines as is typical 

 of younger specimens ; the lateral edges of the rostrum also 

 are nearly smooth instead of strongly dentate as usual. These 

 belong to the variety- described and figured by Dana as A. 

 )t(tbiUs-, but they do not appear to attain a large size, and 

 perhaps develop into the typical form with increased age. 

 Still others from near Stanthorpe, Southern Queensland, have 

 the general chaiacters of the variety uobilis but have the 

 rostrum very large and broader than is usual in the species. 



1 Shaw— Zool. N. Holland, 1794, p. 21, pi. viii. 



2 Dana— Wilkes U.S. Explor. Exped., Crust., i., 1852, p. 526, pi. 

 xxxiii., fig. 3. 



