Yarra Spiny Crayfish, Euastacus yarraensis

Plate 160. The Yarra Spiny Cray-fish, Astocopsis Serratus var. yarraensis (now known as the Yarra Spiny Crayfish, Euastacus yarraensis) found in the Yarra River

Six months after I published in the Second Decade the illustration of the Murray Cray-fish (A. serratus), and about a month after I published in the Third Decade the account of the Yabber Cray-fish (A. bicarinatus), there was published the number of the Proceedings of the Zoological Society of London containing Professor Huxley's remarkable paper on the classification and distribution of the Cray-fish, and I gladly recognize the internal anatomical peculiarity of the Australian Cray-fishes which he has pointed out, characterising his family ParastacidS, peculiar to the Southern Hemisphere, and differing from those of the other half of the world in the podobranchiæ having no lamina, and in the first joint of the abdomen being destitute of appendages in both sexes.

Our plate 160 illustrates a remarkable variety of the typical A. serratus of the Murray, common in the Yarra and its numerous effluents flowing southwards into the sea of the south coast of the colony; and as very few of the inhabitants of these river systems are identical (most of the species and many of the genera being dissimilar), this form is worthy of special note. It is usually less than half the size of the Murray individuals, being usually only five inches and rarely six inches long; it further differs in the whole thorax and abdomen above being of an intense Prussian-blue color, the spines, chelæ, and under surface ivory-white, with the membrane of the joints red. All the proportions and the number and disposition of the spines seem to me to agree so closely with the large pale Murray form, that, although so unlike at first glance, I have no doubt the southern race is merely a variety, which, for convenience of reference, may be distinguished by the name of the river in which it is chiefly found, from its mouth at Melbourne to its highest branches. The colors of those from the Watts River are particularly intense.