BY J. DOUGLAS OGILBY. 13 
its anterior border feebly emarginate, its lateral and posterior 
borders and all the angles broadly rounded, prominently 
arched behind, and like all the marginal shields, smooth ; 
its mesial length is 7 of its greatest width, which is a little 
behind the middle of the shield: second vertebral shield 
similarly shaped, but with the posterior border straighter and 
mesially emarginate, smooth, with two low wide convergent 
ridges running from the first costal sulture to the emargination, 
immediately in front of which the ridges are highest and bear 
a few coarse striz ; between the bases of the ridges the shield 
is markedly depressed, and there is a narrow border of 
fine strize at the front and sides ; its mesial !ength is 2 of its 
greatest width, whichisat the intersection of the first and second 
costals : third vertebra! shield similar in size and shape to the 
second, but with the basai depression vestigial and crossed by 
broad transverse strie, which beyond the ridges become 
longitudinal : fourth much smaller, but with the posterior 
knob stronger, and a median groove anteriorly, otherwise 
as third; its mesial length % of its width at the junction of 
the third and fourth costals : fifth vertebral shield pentagonal, 
the anterior border straight, the outer borders sigmoidal, 
the posterior borders emarginate and meeting at a moderately 
obtuse angle, which almost separates the supracaudals ; the 
prominence is a little behind the middle of the shield, and is 
well developed ; from its front margin two shallow divergent 
grooves extend forwards to the outer ends of the anterior 
border ; its mesial length 3 of its greatest width at the inter- 
section of the fourth costal and third marginofemoral shields. 
First costal shield triangular, with the outer border arcuate, 
the upper concave in front straight behind, and the posterior 
straight, smooth, with scarcely a trace of prominence at the. 
postero-superior angle; its greatest length % of its depth: 
second costal largest, tetragonal, with the outside border 
undulating. the upper feebly convex, and the laterals straight ; 
the postero-superior angle is somewhat prominent and strongly 
rugose, the prominence curving downwards to the middle of 
the lower border as a low wide ridge, the anterior slope of 
which is much more gentle than the posterior ; the anterior 
and outer borders have a narrow marginal band of fine strie, 
inside which are a few very faint coarser striz ; its width 2 of 
its depth: third costal similar to the second, but with the 
