Hi AUSTEALIAN SNAKES. 



be of no use to snakes mo\nng throngli a fluid, and not over a rougli hard 

 surface, and therefore thev are either only rudimentarv or entirely absent. 

 The genus Platiirus, howeyer, is a most remarkable exception, in having 

 ordinary yentral shields ; and this circumstance, together with the lateral 

 position of its nostrils, induce me to believe that these serpents frequently 

 go on shore, sporting or hunting over marshy ground. In many Sea 

 Snakes the hind part of the body is curved and prehensile, so that they 

 are enabled to secure a hold by twisting this part of the body round corals, 

 seaweeds, or any other projecting object. Their tail answers all the pur- 

 poses of the same organ in a fish, and their motions in the water are almost 

 as rapid as they are uncertain and awkward when removed out of their 

 proper element. Their nostrils are placed quite at the top of the snout, 

 as in Crocodiles and in Fresh Water Snakes, so that they are enabled to 

 breathe whilst the entire body and the greater part of the head are im- 

 mersed iu water. These ojienings are small and subcrescentic, and provided 

 Avith a valve interiorly, which is opened during respiration, and closed when 

 the animal dives. Tliey have very capacious lungs, extending backwards 

 to the anus, and consequently all their ribs are employed in performing 

 the I'espiratory function ; by retaining a portion of the air in these exten- 

 sive lungs, they are enabled to float on the surface of the water without 

 the slightest effort. 



"The ' scales' of the Sea Snakes are frequently very different from 

 those of other snakes ; they overlap one another in only a few species 

 {Phiturus, Hydrophis stokesii, and belcheri) ; in others they are but little 

 imbricate and rounded behind, and, again, in others they are of a sub- 

 quadrangular or hexagonal form, placed side by side, like little shields ; 

 the less imbricate they are, the more they have lost the polished surface 

 Avhich we find in other snakes, and are soft, tubercular, sometimes porous. 

 T'he form and the arrangement of the scales attbrd good specific characters, 

 but it is necessary to observe that they generally ditt'er iu size, arrange- 

 ment, and form, in the different parts of the body. In my descriptions I 

 have always counted the series of scales on the neck — that is, at a distance 

 from the head about equal to its length, having found that the numbers at 

 that place are least subject to variation in diflFerent indi^-iduals ; whilst I 

 have taken the characters of the form or arrangement of the scales from 

 those in or behind the middle of the body, the scales on the neck being 

 narrow and more or less imbricated in almost all the species. 



