NO. 1665. 



TWO SPECIES OF FOSSIL TURTLES— II AY 



195 



The nuchal bone is broad, about 55 mm., and is more like that of 

 Boremys than it is like that of Chisternon." The preneural is inter- 

 mediate in size between that of each of the genera just named, being 

 18 mm. along the midline, 24 mm. transversely. The first neural 

 is pyriform, 32 mm. long, 26 mm. wide. A part of the posterior 

 end appears as a small separate bone. Each of the three succeeding 

 neurals has a part missing, making its length somewhat doubtful. 

 On the underside of each first costal there is a thickening which 

 joined the axillary buttress. Fragments show that these buttresses 

 were strongly developed. 



The first vertebral scute is narrow in front, expanding backward 

 to 60 mm. On each side of it there is a small supernumerary scute. 

 The second vertebral scute is TO mm. long and 66 mm. wide. Only 

 a part of the third 

 vertebral is repre- 

 sented. In the cen- 

 ter of the preneural 

 there is a small flat- 

 tened ring, as if 

 there had been here 

 a small scute; but 

 the ring is not con- 

 nected with other 

 sulci. The preneural 

 is not crossed by a 

 sulcus subdividing 

 the first vertebral 

 scute, the latter re- 

 sembling thus that 

 of Boremys. 



The plastron fur- 

 nishes us with knowl- 

 edge of all essential parts, except the hinder lobe. The length of the 

 anterior lobe is 70 mm., its width about 100 mm. Xt each end of the 

 gulohumeral sulcus there is a rather deep notch. The entoplastron is 

 25 mm. long and 10 mm. wide. The mesoplastra are only about 7 mm. 

 wide at the midline, but they expand to 63 m,m. where they join the 

 bridge peripherals. There are small intergulars and rather large 

 gulars, the latter joining along the midline 21 mm. The humerals 

 measure along the midline 10 mm. ; the pectorals, 63 mm. ; the abdomi- 

 nals, 30 mm. These measurements agree more closely with those of 

 Boremys pulchra than with those of either of the species of CJtisternon. 



On the left bridge, the only one represented in the specimen, there 

 are shown three inframarginal scutes; but there was evidently an- 

 other in front of the anterior of the three. 



Fig. 3. — Chisternon? iNTERrosrriM. Part of plastron. 



X g. ent, ENTOPLA.STRON ; epi, EPIPLA-STRON ; hyo, HYO- 

 PLASTRON ; hypo, HYPOPLASTRON ; mes, MESOPLASTRON ; 

 per. 5, FIFTH PERIPHERAL. 



« Fossil Turtles of North America, figs. 72, 76, and 88, 



