148 MEMOIRS OF THE CARNEGIE MUSEUM 



gradually widening to a point a little beyond where the sulcus first reaches the 

 entoplastron, which measures 63 mm. antero-posteriorly, then again narrowing 

 to the midline, where it has a fore-and-aft extent of 40 mm. The pectoro-abdominal 

 sulcus runs straight across the plastron as in Hadrianus corsoni. 



The hyo-hypoplastral suture runs a very tortuous course across the plastron. 

 The hyoplastrals meet on the midline for a distance of 136 mm. The hypoplastrals 

 at the center have a transverse width of 400 mm. 



The pectoral scutes on the midline are less than one-fifth the width of the ab- 

 dominals, and following Hay's analysis of the various species of the genus this 

 proportion would be sufficient to show the specific distinctness of the present speci- 

 men. In the proportions of these scutes the present species is nearest Hadrianus 

 tumidus Hay, which is also from the Uinta formation, and in which the pectoral 

 scutes are less than one-third as wide as the abdominals at the center, but it is 

 distinguished from that species by having a thicker plastron and by the different 

 form of the pectoral scutes, and the greater width posteriorly of the entoplastron. 

 From H. majusculus and H. corsoni the difference in the proportions of the length 

 to the breadth of the anterior lobe will help to separate the present form; that 

 is to say in Hadrianus robustus the length is 77 per cent, of the width at the base, 

 while it is 68 and 71 per cent, respectively in the other two species mentioned above. 



15. Hadrianus utahensis sp. nov. 

 Plate XXVI, fig. 1; text-fig. 20. 



Type : C. M. No. 2343, consisting of the plastron and portions of the periph- 

 erals above the bridge on the right side. The anterior portion of the lip, and 

 parts of the margins of both anterior and posterior lobes are missing. Collected 

 by Earl Douglass, July 30, 1908. 



Locality : South of Kennedy's Hole, Uinta Basin, Uinta County, Utah. 



Horizon : Horizon B or C, Uinta formation. Upper Eocene. 



The plastron of the type specimen is estimated to have had a greatest length 

 of about 520 mm., and a greatest width at the center of 320 mm. The anterior 

 lobe is about 175 mm. long and 300 mm. wide at the base. The width of the lip, 

 where the gular sulci cross the free border, is 110 mm. The plastron is quite 

 concave, indicating that the specimen was in all probability a male. 



While every thing indicates that the hp extended well forward, it probably 

 continued the general contour of the lobe. The free borders of the lobe are sub- 

 acute, being bevelled off from the upper surface, so that the edge is nearly on a 

 level with the ventral surface of the plastron. At the center on the broken border 



