BOTHREMYDID.S. 



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right eleventh peripheral and nowhere else. With it is connected a portion of the pygal. The 

 proximal half of the left sixth costal is now missing. On the other hand, the distal end of the 

 right seventh costal has been found and included in the figure. 



The individual was a large one, the length of the carapace being estimated at 650 mm. 

 Cope states that his figure is one-third the natural size, but in reality it is in width only a little 

 more than twenty-two hundredths of the original. As regards the length of his figure, it is 

 much foreshortened. 



As in the other species, the costals of the last two pairs (fig. 99) meet at the midline. The 

 eighth neural was not developt and the seventh was short. The sixth costals are 66 mm. wide 

 at their distal ends; the seventh, 70 mm., the eighth, 54 mm. The sixth is 9 mm. thick where 

 it joined the neural; 5 mm. at the distal end. 



The suprapygal, described by Cope under the name of pygal, is triangular, pointed above, 

 83 mm. long and 99 mm. wide behind. The eleventh peripheral measures 72 mm. along the free 

 border and is 65 mm. high. The free edge is acute. It is slightly thicker at the hinder end than 

 in front, being 10 mm. posteriorly. 



Fragments of two bridge peripherals are present. One, probably belonging near the 

 hinder end of the bridge, has the two faces meeting with an angle of about 50 degrees between 



FIG. 100. Taphrosphys sulcatus. Under side of rear of carapace. X^. No. 1468 A. M. N. H. 



A A, excavated area for ilium; x, sacral rib. 



them at,one end, probably the anterior. At the other end the faces meet at an angle of about 

 30 mm., the free border being acute. The other fragment has the two faces meeting at an angle 

 of about 90. This bone probably belonged near the front end of the bridge. 



As Cope states, the sculpture of the upper surface of the carapace is coarsely reticulate, 

 tending to enclose areas longitudinal with the costals toward their middle and distal portions, 

 while that of the peripherals is closer. The sulci are shallow and narrow. The fourth vertebral 

 scute was about no mm. long and 154 mm. wide; the fifth was no mm. long, 162 mm. wide, 

 only 50 mm. anteriorly. Its lateral extremities are sharply angled. The costo-marginal sulci, 

 so far as they are represented, are confined to the peripherals. 



On the inferior surface of the carapace (fig. 100) we find, excavated partly in the seventh, 

 partly in the eighth costals, a large pit, 78 mm. long and 28 mm. wide, for the reception of the 

 upper end of the ilium. The pit is bounded anteriorly by a sharp ridge proceeding from the 

 rib-head of the seventh costal. This ridge is highest at the upper end, lowest in the middle. 

 Behind, the pit is bounded by a low rough ridge running along the middle of the eighth costal. 

 Both the costals are much thickened at the lower end of the pit. The upper end of the pit is 

 inclosed in front by a low ridge derived from the base of the rib-head of each costal; behind, 

 by a distinct squarish bone, which is to be regarded as the tenth dorsal rib, corresponding to the 



