92 RECORDS OF THE AUSTRALIAN MUSEUM. special kno\yledge, is particularly valuable — it was agreed that the moth represented sitting on a tree-trunk forcibly reminded one of the head of the tree lizards, members of the genus Varamifi. An example is depicted on the plate. It is the "eye" on the wing of the moth that strikes the key-note of the situation ; but in addition the shape of the wing, when the moth is resting, looks very suggescive. The moth is one which passes its larval state in the butts of Eucalyptus trees for the period of live or six years, but on emergence the perfect insect is not prone to tly, and would therefore be very liable to be attacked by birds. Hence the probability that my surmise of the striking resemblance to the head of the lizard being an instance of genuine protective imitation is correct. The reptile photographed was not very specially selected, and others might perhaps have been used wherein certain features were more strongly marked. For instance, many members of the genus Varanus have a dark line passing from the eye backwards. In conclusion, it might be well to point out that the marks on the outer margin of the visible wing of the moth are very suggestive of labials, while the various lines in front savor of the regularity of scales. Some of these tree-lizards and the moth are natives of New South "Wales. The log from which the moth figured emerged was collected near Newcastle, by Mr. AV. Kershaw, late of the Melbourne Museum, and kindly presented to this Museum, thus affording us an opportunity of observing the living moth in its natural position and development. Some SUGGESTIONS REGARDING the FORMATION of "ENHYDROS" oh WATER-STONES. By T. CooKSEY, Ph. D., B. Sc. (Mineralogist to the Australian Museum.) The mode of formation of these interesting bodies is still in considerable doubt, and therefore it seems to the writer that these notes attempting to explain their occurrence will not be without interest. Mr. E. J. Dunn has given a description of the characters of those specimens which he obtained from Spring Creek, Beech worth,
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