88 AUSTRALIAN SNAKES. 
Synopsis of the Genera. 
A. Ventral shields well developed, flat. 
Two pairs of frontal shields ... a eas ie a ... Platurus. 
B. Ventral shields well developed, with a median ridge. 
Scales imbricate ae 28 ss re be ne ... Aipysurus. 
C. Ventral shields large, with a very slight median ridge. 
Labial shields reduced to three above and below ; scales imbricate, 
strongly tuberculated ... wh igs sie Gs ... Emydocephalus. 
D. Ventral shields narrow, or rudimentary, or absent. 
*Nasals separated by frontal shields. 
Ventral shields distinct to the vent ... be _ can ... Disteira. 
** Nasals contiguous. 
Head covered with scales behind... 24 aes .. Acalyptus. 
Head short or of moderate length, entirely dlielded: lower jaw 
without notch in front ... 4 ae . Hydrophis. 
Head of moderate length, suet shielded ; lower jaw v deeply 
notched in front ... ae ie be vad st .. Enhydrina. 
Snout very long, spatulate ... ae es we Ge ... Pelamis. 
PLATURUS, Latr. 
Body subcylindrical, of moderate length. Shields of the head 
subnormal in number and arrangement; nostrils lateral, in a single 
nasal shield, both nasals being separated from each other by a pair of 
anterior frontals. Scales imbricate, smooth; ventral shields well developed. 
tail with two series of subcaudals. 
This genus approaches the Land Snakes in several characters. 
The shields of the head are very regularly disposed ; there are two pairs of 
frontals, frequently with an azygos shield between the hind pair. The 
nostril is lateral, piercing a narrow nasal shield; loreal absent. One pre 
and two post oculars. Seven upper labials, the third and fourth of which 
enter the orbit; temporals scale-like 1+2+8. The throat is covered by 
two pairs of chin-shields anteriorly and by scales posteriorly, the ventrals 
commencing at some distance behind the head. The scales are regularly 
imbricate, smooth, short, slightly rounded behind; the number of longi- 
tudinal series on the body varies much, from nineteen to twenty-five, in 
different individuals, without affording a character for specific distinction ; 
it is more constant on the front part of the trunk. The ventral shields 
