BOTHREMYDID&. 121 
was acute or obtuse; but the probability is that it was acute. At one point it runs down to a 
thickness of only 11.5 mm. The fore-and-aft extent of the bone is 84 mm. ‘The anterior 
border is very thick, 52 mm. at one section; and is excavated to form a part of the sternal 
chamber. The hinder border was not more than 15 mm. thick. The upper border joined the 
ends of 2 costal bones, proof that the peripheral does not belong to the axillary region of the 
left side. “ 
Figure 122 is a section which is taken 20 mm. to the left of the front border. The costal 
that articulated with the anterior half overlapt the peripheral, but the succeeding one was 
overlapt by the peripheral. Satisfactory contact is not obtained between the peripheral here 
described and the fifth costal above described, so that their exact relations are not known. 
The upper surface of the peripheral (fig. 121) is ornamented by a network of grooves 
similar to those of the costal, but forming a much closer reticulation. That portion of the 
inferior surface of the peripheral covered by horn has a still closer network of grooves. On the 
upper surface is seen a triradiate sulcus, which bounds a portion of the third costal scute and 
portions of two marginals. 
Fig. 123 represents the entoplastron. Its length is 84 mm.; its width, 109 mm.;_ its 
greatest thickness, 14 mm. In the hinder border is a constriction. The outer surface presents 
neither sculpture nor distinct traces of sulci. 
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Fics. 121-124.—T aphros phys dares. Parts of the type. x 4. No. Li2y A. M.N.H. 
121. Seventh or eighth peripheral, upper surface. 123. Entoplastron 
122. Section of peripheral of fig. 121. 124. Section along hypoxiphiplastral suture. 
The left xiphiplastron is present from the anterior border to the hinder end of the pubic 
scar. Its greatest width is 140 mm.; so that the hinder lobe was 280 mm. wide at the hypo- 
xiphiplastral suture. This suture was, as seen from below, a very close one; seen from above, 
the adjoining bones sent coarse digitations into each other. The anterior end of the right 
xiphiplastron overlapt the left as much as 28 mm. The median suture was jagged above, 
but more even on the under side. Near the antero-median angle the bone is 17 mm. thick; 
the postero-median portion, 12 mm. The free border, for some distance behind the hypo- 
xiphiplastral suture, is thin and acute. Fig. 124 is a section taken near the suture. The notch 
in the upper surface was filled by a digitation from the hypoplastron. On the upper surface 
of the bone is a large elevated area which articulated with the pubis. This articulation is 
much eroded. Its length was about 66 mm.; its width, about 27 mm. The lower surface of 
the bone shows no distinct sculpture. The femoro-anal sulcus crosses the bone, beginning at 
the median line about 45 mm. behind the hypoxiphiplastral suture and meeting the free border 
about 66 mm. behind the suture. 
What appears to be a portion of the right xiphiplastron is preserved. It bears the elevated 
articulation for the ischium. On the left is a part of the median suture. The articulation for 
the ischium is about 48 mm. long and 17 mm. wide. Unless there is some error regarding this 
bone, the notch in the hinder lobe must have been quite different from that of the other species 
of the genus. 
