428 OLIVEE p. HAY 



presence of this bone confirms the conclusion that was reached 

 regarding these bones on the neurals of the specimen in the 

 United States National Museum. 



On the third neural of this specimen, at the rear of the second 

 vertebral scute, there is an area which is rough and pitted, but 

 no overlying plate of bone is found. This has probably been 

 completely absorbed. A smaller similar area is seen at the rear 

 of the first vertebral scute, on the first neural. Near the rear of 

 the fourth vertebral scute, on the peak of the high ridge there 

 is found, lying also partly on the seventh neural and partly on the 

 eighth, a patch which is very uneven and deeply pitted; but 

 if there was ever an overlying plate of bone there it is now gone. 

 On the hinder part of the narrow ridge of the surface occupied 

 by the vertebral scute is a long rough tract, but no overlying 

 bone is found. 



Coming now to the costal bones, attention w^ill be given first 

 to the fourth of the right side, that costal into which is inserted 

 the buttress of the right hypoplastron. Capping the summit of 

 the boss forming a part of the lateral keel and near the rear of the 

 second costal scute area is a plate of bone (fig. 3) distinctly sutured 

 to the underlying costal. It is about 15 mm. long and nearly 

 as wide. Where it comes to the suture between the third and 

 fourth costal bones, it is nearly 4 mm. thick. On the corre- 

 sponding elevation of the left fourth costal there is a pitted area 

 similar in size and shape to that on the right side, but the cap of 

 bone has either been absorbed or has fallen off during macera- 

 tion. One cannot doubt that it was at some time present. Com- 

 ing forward to the boss at the rear of the first costal scute area, 

 on the second costal bone, we find a rough and deeply pitted 

 area much hke that found on the fourth costal, but no plate of 

 bone caps it. The impression is again given that this plate has 

 been lost in maceration. It appears to have extended forward 

 on the first costal bone. On the corresponding boss on the right 

 side is a surface in size and shape like that of the left side, but it 

 is smoother. The bosses near the rear of the third and fourth 

 costal scute areas indicate that they may once have been fur- 

 nished with thin plates of bone, but of these there are now no 

 traces. 



