PTYODACTYLUS HASSELQUISTII. 71 
of the first section the nostril is swollen in a varying degree, and is denned by the 
rostral, first labial, and three nasals. In two out of the number tabulated the first 
labial is excluded, whereas in four the asymmetrical formula E,. L. 3 N. and L. 3 N. is 
present. In the second section the nostril, instead of being merely swollen, rises above 
the snout as a short tubular orifice defined by the first labial and three nasals. The 
geckos, however, from the Plain of Suez by their semitubular or much swollen nostrils 
link the geckos with essentially tubular nostrils to those of the merely swollen type 
found in the Sinaitic Peninsula, Syria, and Eastern Arabia. 
In those asymmetrical nostrils the nostril with the formula L. 3 N. is never tubular, 
so that there are other factors at work in the production of a tubular nostril besides 
the mere presence of the shields in question. The tubularity in the second section 
of Phalanx II. appears to be brought about primarily by the considerable vertical 
extension of the nasal process of the first labial, which rises above the level of the 
rostral, and the concomitant nearly vertical expansion of the nasals. The exclusion of 
the rostral among the members of the first section is apparently due to slight variations 
in the breadth of the nasal processes of the rostral and of the first labial and of the 
anterior upper nasal. If the nasal process of the second of these shields is large and 
that of the first small, the former abuts against the upper nasal and so shuts out the 
rostral ; on the other hand, a reduction in the size of the nasal process of the first 
labial gives rise to the formula R. 3 N. ; whereas if the nasal processes of the 
rostral and first labial are small, the nasals exclude them from taking any part in 
the formation of the nostril, and the formula 3 N. results, as in the well-marked 
P. Iwmolepis, Blanfd., of which, however, only a few examples are known. 
In the varieties oudrii and ragazzi there are no exceptions to the formula R. L. 3 N., 
which, with the exceptions indicated, is the prevailing formula throughout the 
species. 
All the geckos of the second Phalanx have more or less what can only be described 
as a tough skin compared with the generally soft skin of the members of the first 
Phalanx. Among the latter, however, an individual may now and again be met with 
having its skin almost identical in texture with the skin of the second Phalanx. 
The specimens I have met with are extremely few, and it is noteworthy that they have 
been found in the open desert, whereas the softest-skinned geckos are encountered in 
the recesses of monuments and temples and in houses ; but whether these differences 
in the habits of life are sufficient to account for the dermal modification remains to be 
ascertained. The skin, however, of the geckos of the second Phalanx becomes coarser 
in Syria than it is in the Plain of Suez. 
There can be no doubt that the range of variation in the Sinaitic Peninsula and in 
Southern and Northern Syria is much greater than what prevails in the first Phalanx. 
This is very manifest in a number of details, even in the general form of the body 
itself. The lizard fig. 4 (Plate VI.) has almost the character of the body of the typical 
