ON THE DERMAL ARMOUR OF JACARE AND CAIMAN 305. 
Again, in the genera Ad/zgator, Crocodilus, Mecistops, Rhynchosuchus,, 
and Gavzalis, the edges of the scutes, except those of the two median 
longitudinal rows, are hardly ever united by sutures, nor do the 
posterior margins of those in each transverse row overlap the anterior 
margins of the succeeding row. At any rate, there is no flat, bevelled, 
articular facet on the outer surface of the anterior margin of a scute,. 
for articulation with the inner surface of the posterior margin of its. 
predecessor. In the genera Cazman and /acare, however, the lateral 
edges of all the scutes of the dorsal and ventral shields are united by 
serrated sutures; and the anterior end of the outer face of each is 
provided with a well-marked smooth facet, which is overlapped by 
the smooth under-surface of the scute in front of it. 
I first noticed the remarkable structure of the dermal armour of 
these Adigator7ide in the skin of a /acare (sp. incerta), wanting the 
end of the tail, but which must have belonged to an animal between 
five and six feetin length. It had long been in my possession ; but I 
had never before had occasion to study its characters minutely. 
The horny scales, which had the appearance of thin tortoise-shell,. 
could be readily peeled off (especially by the aid of a little caustic 
potash) ; and then the white surface of the subjacent bony scute upon 
which they were modelled came into view. It is to be understood, 
however, that the inner surface of the scale corresponded only in its. 
general form with the outer surface of the scute ; for it did not dip 
into the pits with which the latter is sculptured. These are in fact 
filled by the dry dermis which extends over and encloses the scute, a 
very thin layer (bearing the rete mucosum) being interposed between 
it and the scale ; so that the pitted sculpture does not come out well 
until the scutes have been boiled. 
The dorsal scutes are both carinated and angulated. By the ap- 
plication of the former term, I mean to indicate that, along a median 
or submedian longitudinal line, their substance is more or less elevated, 
so as, in many cases, to form a very prominent crest, This crest 
always subsides before it reaches the anterior margin of the scute, 
though it may extend beyond the posterior margin. Its highest 
point is always behind the centre of the scute, and is devoid of sculp- 
ture. The sculpture however seems to radiate from this point, inas- 
much as it consists, on the greater part of the scute, of distinct pits, 
which are usually round towards the centre, but towards the periphery 
become ovals with their long axes directed towards the point in 
question. 
The smooth inner surfaces of the scute shelve towards a depression 
VOL. II x 
