32 



either absent or merged into' the neighbouring shields. 

 But in the harmless snakes it is present, as a rule, and in 

 some it is double or triple (Ptyas, Zaocys.) Sometimes 

 it wedges itself between the preoculars into the orbit ; and 

 conversely a preocular sometimes wedges it out from contact 

 with the labials. This irregularity is frequently found in 

 Tropidonotus plumbicolor. 



The preoculars (or preorbitals) are variable in number ; 

 one or two is the usual number ; the upper is generally the 

 larger and often reaches on to the crown, and more rarely 

 as far as the vertical ; the lower is smaller and often seems 

 to be a fragment of a lower labial. The postoculars 

 number usually from one to three, and extend lower down 

 than the preoculars. The lower border of the orbit is 

 sometimes occupied by a subocular, but this completion of 

 the orbital ring is rare (Zamenis, certain HomalopsidcB and 

 AmblycephalidcB) ;* the rule is for one or more labials to 

 enter the orbit. 



Behind the postoculars are the temporals, variable in 

 number, shape, and arrangement. They are counted back- 

 wards in vertical rows ; thus "2 + 2 + 3 temporals" means 

 that behind the postoculars are two shields, one over the 

 other, then two more, similarly placed, and lastly a set of 

 three. They sometimes have to be counted thus | + J 

 this verges on total irregularity. 



s > 



These temporals are often irregular as they are transi- 

 tional to ordinary scales. In one snake (Ophiophagus) the 

 temporals join in a complete ring round the occipitals by 

 the addition of two large shields behind them. This some- 

 times occurs in the cobra, a snake to which Ophiophagus 

 is closely related. 



* I have observed this once in a cobra"; it was an aberrant 

 specimen in other respects. See note to Naga, Part III. 



