93 



The scutes in front of the first vertebral are more symmetrically arranged than in Baena 

 hatcheri; but in Baena and possibly in Boremys these scutes are subject to great variation. 

 The vertebrals are slightly longer than broad. In B. hatcheri they are much broader than long. 

 There is an accessory, or supernumerary, costal scute on each side of the first vertebral. In 

 species of Baena one or both of these may be absent. The presence of large supramarginals 

 (fig. 88, srri) is surprising. In Macrochelys there are three or four of these on each side; but 

 these are comparable in size and position with the marginals. In Boremys puhhra, on the 

 contrary, the supramarginals are as long fore and aft as are the costals and alternate with them. 



The plastron (fig. 89) has a length of about 172 mm. The anterior lobe is slightly narrower 

 than that of B. hatcheri. The entoplastron is long and narrow. The bridge is somewhat 

 narrower relatively to the length of the plastron than in B. hatcheri. The mesoplastra join 

 along the midline for a space of about 14 mm. The hinder lobe seems to differ little from that 

 of the species just mentioned. The intergulars are small and do not reach back on the ento- 

 plastron, thus differing from those of B. hatcheri. 



FlG. 89. Boremys puhhra. Plastron of type. X^. From Lambe's figure. 

 Genus NEURANKYLUS Lambe. 



A genus of uncertain position and known only from a portion of the carapace of the type 

 species. Eighth neural large, followed by an expanded suprapygal. In the type a ninth pair 

 of costal bones. The vertebral scutes nearly twice as wide as long. 



Type: Neurankylus eximius Lambe. 



This genus is placed provisionally in the Baenidte. When the last neural of Neurankylus 

 eximius is compared with that of Baena riparia they are seen to be very similar. The pre- 

 ceding neural in the latter species is elongated and appears to occupy the place of two neurals; 

 and it is possible that the sixth and seventh neurals of Lambe's figures were consolidated. The 

 presence of the ninth pair of costals is probably an individual variation and of no classificatory 

 value, as suggested by the Yale specimen of Echmatemyswyomingensis(Le\dy'), which possesses 

 ten pairs of costals. The very broad vertebral scutes indicate that the genus is distinct 

 from Baena. Mr. Lambe placed the genus provisionally among the Chelydrida;, but as no 

 genera of this family are known from deposits older than the Tertiary and as the type has some 



