16 THE ROYAL SOCIETY OF CANADA 



in breadth according to their position on the periphery. In the 

 front half of the carapace they are longer than broad with the exception 

 of the first which is triangular and very small. The eighth, ninth 

 and tenth are broader than long; in the eleventh and twelfth the 

 reverse is the case. 



The reader is referred to the accompanying figure for a general 

 idea of the shape of the carapace as well as for the relative size and 

 disposition of the bones and scutes. 



Of the vertebral scutes the first is nearly twice as broad as 

 long, in the second the length and breadth are about equal, in the 

 third the length slightly exceeds the breadth, and the fourth and 

 fifth are broader than long. Their transverse sulci cross the first, 

 third, fifth and seventh neural bones. The breadth of the nuchal 

 scute is about four times its length. 



The four larger costal scutes are all broader than long notwith- 

 standing the intervention of the three supramarginals between them 

 and the marginals. The presence of additional costal scutes, one in 

 advance of the first costal, the other behind the fourth, lessens the 

 length principally of the first and fourth scutes. The anterior super- 

 numerary costal is somewhat triangular in shape, the posterior one is 

 irregularly oval, or sub-circular. 



The three supramarginal scutes are long in comparison with their 

 breadth, and are in a row, alternating with the costal scutes, between 

 them and the marginals. 



The marginal scutes are all longer than broad. Those which 

 bound the supramarginals outwardly are noticeably reduced in breadth, 

 the largest being the third and the ninth, in advance of the first supra- 

 marginal and posterior to the third respectively. The inner sulcus 

 of the tenth marginal scute overlies, or corresponds in direction with, 

 the suture between the eleventh marginal and eighth costal bones. 



The space occupied by the supramarginal scutes seems to have 

 affected the breadth of the marginal scutes to a greater extent than it 

 has that of the vertebral and costal scutes. The presence of supra- 

 marginals probably accounts to some extent for the breadth of the 

 carapace in comparison with its length. 



The carapace of Boremys pulchra is remarkable for the presence 

 in it, on each side, of three supramarginal scutes, and two supernumer- 

 ary costal scutes. The suprapygal bone between the eighth neural 

 and the pygal repeats posteriorly what is found anteriorly, viz.. 

 the intervention of the preneural between the first neural and the nuchal. 

 In front there is the separation of the preneural from the first neural, 

 and posteriorly the suprapygal from the eighth neural. Attention is 

 again directed to the sculpture of the carapace. 



