166 



THE EXTINCT BATKACHIA, REFHLIA 



The plastron of tins species is relatively much thinner than in the other species of the genus. 

 A sternum, probably, of this species, is in my collection. It is unfortunately without the xiphisternal pieces, but 

 conforms in all respects with what we know of P. sulcatus. Its surface has been injured by pyrites. It is character- 

 Fig. 45. ized by its thinness and general lightness, as well as 



by the singular form of the hyostcrnal element. 

 The remains consist of a largo portion of the plas- 

 tron, and two costal bones, found in the marl ex- 

 cavations of the West Jersey Company, near Barnes- 

 boro. 



The external surface of the plastron exhibits 

 neither sculpture nor impression of sutures of 

 scutes. It is slightly rugose in some places. The 

 free margin at the axillary and inguinal regions is 

 obtuse, but becomes thin a little distance before 

 reaching the epistcrnal and xiphisternal sutures, re- 

 spectively. 



The suture between the hyo- and hyposternals is 

 straight and fine, while that between hypo- and xi- 

 phisternals is straight and coarse. The longitudinal 

 median suture is irregular and very coarse. That 

 between hyo- and epistennim is remarkable in its 

 direction, thus distinguishing the species from Ado- 

 cus pravus, with which this plastron might oth- 

 erwise be, compared. It advances posteriorly on the 

 outer part of the hyostcrnal, causing its junction with 

 the margin to be an inch behind its junction with the 

 mesosternum ; the reverse is the usual relation in 

 tortoises. 



The bones of the plastron, while more than hall" 

 as wide again as those of A. beatus, arc medt 

 ally scarcely half so thick; the thickness increases to 

 within a certain distance of the outer margin. 



The accompanying restoration of the plastron is 

 nu-rely ,1, 'signed to illustrate the form and characters of the sutures described. The outlines of the mesosternum are 

 erroneous; the piece is longitudinal, not tranverse; it had not been obtained at the time the cut was made. 



Measurements. 

 Total width plastron externally, within elevations of bridges, 

 Length hyosternal, on margins, from first rise at axilla to cpisternal suture, 

 From latter to mesosternal suture, 

 Thickness hyosternal at middle sut., 

 " hypostcrnal " " 



In. 



Lin. 



11 



10. 



3 



8. 



1 



10.75 





4.25 





2.8 



TAPHROSPHYS LBSLIANUS, Cope. 



m 



This is a smaller and more delicate species than the last, and differs in many particulars. It is found on a, single 

 individual, which, though not more than half the size of the T. sulcatus, is evidently adult. The portions preserved 

 arc a considerable number of the element of carapace and plastron, but none other. The union of the costal and 

 marginal bones is complete. The first costal has the same form as in T. molops, bearing as usual, a crest representing 



