I II 



130 G. H. Wieland — Upper Cretaceous Turtles. 



stress upon the fact that the nearest relatives of this turtle and 

 its congeners are, so far as yet present in existing faunas, now 

 mainly to be found in far southern lands. The species is next 

 related to Propleura (Os'teopygis) erosa of Cope, and to the 

 type of the genus Propleura (Osteopygis) sopita as further 

 noted below. 



The arrangement of the plates and horn shields approaches 

 that of Osteopygis, but there are many differences, the citation 

 of which following the notes already made on this genus will 

 answer quite fully the purposes of description. The differ- 

 ences follow : — 



(a) The surface of the bones of the Carapace is not smooth 

 to line lined, as in Osteopygis, but coarsely round pitted to 

 uneven depths, as if by numerous rain drop impressions of 

 different sizes. Comparison of the surface of' the various 

 parts of the skeleton shows that while there are pittings pres- 

 ent that may be ascribed to accidents of preservation, the 

 characteristic pitting of the Carapace as shown in the plate is 

 a true surface sculpturing. The pits are from 1 to 6 mm across, 

 and from 1 to 3 or 4 mm deep, the average size being about 3 mm 

 in diameter by 2 mm in depth. 



(b) The proportion of the carapacial parts is quite different 

 from that seen in Osteopygis. The nuchal has much more 

 anterior concave curvature than in 0. Gibbi, and though 

 scarcely broader or longer, is nearly twice as thick. Contrari- 

 wise, the relatively much heavier second marginals are longer. 



(c) The external border of the 6th and 7th marginals is 

 notched at the boundary line of the horn shields, not unbroken 

 as in 0. Gibbi. 



(d) The interior borders of "the marginals present, following 

 the anterior two-thirds of the second, which like all that of the 

 first unites with the 1st pleural by suture, are smooth. Also 

 the outer corners of the rib plates following the first end in 

 oblique smooth edges, thus forming a series of well marked 

 lateral or pleuro-marginal fontanelles, which lie opposite the 

 marginal junctions beginning with the 2d and 3d, and likely 

 extending to the 9th and 10th. These are of broad crescentic 

 outline, and the one bounded by the 6th and 7th marginals 

 and the 4th and 5th pleurals is 7 cm long and about half as wide. 

 See Plate IX. There are no pleuro-marginal fontanelles in 

 the distinctly smaller turtle Osteopygis Gibbi, and probably 

 none in any specimen justly referable to the genus. Such 

 fontanelles formed at the outer edges of the pleuralia consti- 

 tute an anatomical feature that is quite different from the mar- 

 ginal notch over the 3d-9th rib tips as in Osteopygis. 



(e) The rib pits are of rounded conical shape, and not flat- 

 tened. 



