feet. 



inches. 



5 



7 



4 



8 



7 



4 



3 



2^ 



Z 4 



260 GEOLOGICAL MEMOIRS. 



united together at their margins by sutures : smooth on the inner 

 surface where the sutures are most conspicuous, rough and sculp- 

 tured on the external surface according to a definite pattern 

 characteristic of the species, the whole forming a symmetrical, 

 oval, convex, bony case or shell which covered and defended the 

 upper and lateral parts of the entire trunk of the animal. 

 The following are the dimensions of this carapace : — 



Length, following the curve of the back - 



Ditto in a straight line, or the chord of the arc 

 Breadth, following the curve of the middle of the back 

 Ditto in a straight line, or the chord of the arc 



Ditto of the anterior outlet or arched margin at the base of") 1 _ 



the arch - - - - - - -J 



Ditto of the posterior outlet, at do. - - - 1 8 



The component ossicles support on their outer surface a central, 

 large, subpentagonal or subcircular flattened eminence, surrounded 

 generally by five or six smaller discs ; both being rough, but espe- 

 cially the peripheral ones. In the ossicles near the margins of the 

 carapace the middle eminence increases, whilst the peripheral 

 tubercles diminish or disappear. At the anterior margin the 

 middle eminence extends outwards and forwards as a transversely 

 oblong obtuse projection ; at the lower margins near the posterior 

 part of the carapace it extends outwards in the form of an angular 

 process : the ossicles at the posterior margin are the largest, and 

 have a pentagonal shield-shaped figure ; the two smaller sides 

 being wedged into the interspace of the two ossicles of the penulti- 

 mate row. 



None of the ossicles are modified, as in the smaller Armadillos, 

 to form transverse bands connected together by moveable joints, 

 and allowing the carapace to be closed over the retracted head and 

 legs : such a defensive modification of the bony armour was not 

 required for the gigantic G-lyptodon. 



There are forty-four transverse series of ossicles in the present 

 carapace which extend from above, downwards and obliquely back- 

 wards : the longest series at the middle and broadest part of the 

 carapace contain each seventy ossicles ; the number gradually 

 decreasing, as the carapace contracts in width towards the two 

 extremities, the anterior margin being composed of sixteen ossicles, 

 the posterior one of twenty -five ossicles : the total number of these 

 dermal bones may be estimated at above two thousand in the cara- 

 pace of the trunk of the Glyptodon clavipes. To these, in the 

 consideration of the dermo-skeleton of the extinct species, must 

 be added the casque defending the head and the verticillate armour 

 of the short and thick tail. 



3. The tail. The fossil tail of this animal measures one foot 

 six inches in length, is almost circular at its base, and becomes 

 slightly depressed towards its apex ; it is gently curved with the 

 concavity upwards through its whole extent, and consists of a 



