AUSTRALIAN SNAKES. 21 
Ventral and sub-caudal plates margined with dark grey in some 
specimens; the back sometimes more or less marked with darker scales, 
forming a series of reticulated loops; these markings occur in grey-colored 
subjects ; in those of a brown color the marks are not visible. 
* The Australian Fresh-water Snake differs much at various seasons, 
and is either grey or of a rich brown color with salmon-tinted abdominal 
plates, which on the sides are generally red spotted ; there are fifteen rows 
of scales upon the back, each furnished with a raised keel, whilst the 
venomous Zropidechis, which resembles the harmless fresh-water snake, has 
more than twenty rows of very narrow elongate keeled scales on its body. 
Port Essington and North-west Australia are given (by Giimther) 
as the habitat of this snake, its most southern limit being, in all probability, 
the Clarence River. The Museum is in possession of specimens from 
almost every part of Eastern Australia north of the Clarence; and my 
excellent colleague, Mr. George Masters, informs me that, just at dusk, 
large numbers of these snakes were observed at lagoons or waterholes 
where he was encamped, not long ago, in the Wide Bay District ; he never 
noticed them, however, during the middle of the day. 
FAMILY OF TRUE FRESH-WATER SNAKES—~HOMALOPSID. 
Body moderate, cylindrical or slightly compressed ; head rather thick, 
broad, and not very distinct from neck; tail strong, of moderate length, 
tapering, more or less prehensile and compressed at its root, especially in 
the males. Ventral plates narrow, those beneath the tail two-rowed; eye 
small. The nostrils are situated anteriorly on the upper surface of the head, 
small, and provided with a valvule. Dr. Giinther, from whose writings 
the above is abridged, mentions, with regard to the habits of these 
reptiles (which are not met with except in the far north of Tropical Aus- 
tralia), that they are thoroughly aquatic, and only occasionally found on the 
beach. In their organization they approach the true marine snakes, and are 
easily recognizable by the position of the nostrils on top of the snout, 
which enable them to breathe by raising a small part of the head out 
of water. The same arrangement is common to crocodiles, sea-snakes, 
and other aquatic animals. Many have a distinct prehensile tail, by 
