ON THE DERMAL ARMOUR OF JACARE AND CAIMAN 307 
-outer edges of the outermost ventral scutes thin off and are not united 
with any bony element; and the ventral, like the dorsal scutes, are 
usually arranged symmetrically on either side of the median sutural 
line, There may be as many as twenty-two scutes united by their 
lateral sutures into a single strong, curved, transverse, bony, bar-like 
segment of the ventral armour. 
Throughout the neck and body, and as far as the commencement 
-of the tail, the ends of the dorsal and ventral bony bars, whose sum 
may be regarded as a dorsal and a ventral shield respectively, are 
separated by an interval of integument, in which only small scattered 
scutes are visible. The physiological import of this arrangement 
becomes obvious when we consider in what manner the animal 
breathes ; and indeed the integumentary interval answers very pre- 
‘cisely to the leather which connects the two boards of a bellows. 
Again, though the limbs are themselves covered with articulated 
scutes, they are afforded free play upon the body by this flexible 
interspace. Immediately behind the hind legs, the ventral and dorsa] 
Shields unite ; and the tail is from that point surrounded by a succes- 
-sion of bony hoops, each of which corresponds with a vertebra, the 
segments of the exo-skeleton answering to those of the endo- 
skeleton. 
The most remarkable feature about the ventral scutes, however, 
and that in which they differ most widely from the dorsal ones, con- 
sists in the fact that each scute is composed of two distinct pieces, an 
anterior and a posterior, which unite together by a transverse serrated 
suture. The anterior piece or “semi-scute” may attain to three- 
‘quarters the length of the posterior, and it has exactly the same 
width. The anterior semi-scute bears the articular facet and the 
transverse pitted groove, whose posterior wall is just in front of its 
hinder edge, or in other words, of the suture, when the two semi- 
-scutes are united. 
Such are the general characters and mode of arrangement of the 
dorsal and ventral armour of /acare. But there remain many note- 
worthy peculiarities in the disposition and number of the components 
‘of each band of the armour. 
. Thus, in the dorsal shield there are two rows of nuchal scutes, each 
containing eight separate keeled bony plates ; and of cervical scutes 
there are five rows, the two anterior of which contain four angulated 
and carinated scutes each, while the three posterior contain only two 
scutes each, All these scutes, except the anterior row, have articular 
facets; and all those of each row are united suturally. Of dorsal 
scutes there are thirty transverse rows up to the median keel of the 
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