101 



the hinder lobe is not given, but its posterior extremity was 35 mm. wide, truncated, and 

 with rounded angles. It was shorter than the anterior lobe. Its thickness in the inguinal 

 region was 10 mm. 



The surface of the plastron was obsoletely, but coarsely, rugose; roughest in front, where 

 the sculpture consisted of short, raised lines irregularly disposed. 



The intergulars were distinct. These were followed by a pair of interhumerals, which were 

 longer than wide and crowded the humerals away from each other, and they seem to have 

 extended themselves backward between the pectorals likewise. The pectoro-humeral sulcus 

 appears to have been advanced well forward. Cope states that it was impossible to determine 

 whether or not "intermarginal " scutes were present, and that if they existed their position was 

 quite external. It is probable that by "intermargmals" was meant inframargmals. 



The carapace is stated to have possest an openly dentate posterior border. The surface 

 was irregularly swollen, especially along the margins of the vertebral scutes. The latter were 

 wide; the marginals are said to be narrow, by which is probably meant that they rose but a 

 short distance from the free margins. 



The description of this species given by Cope indicates that it was related to Baena rather 

 than to Adocus. The thoro co-ossification of the bones, so that the presence of mesoplastrals 

 could not be proved or disproved, the uneven surfaces of the shell, the notcht border of the 

 carapace, all point toward Baena. At the same time, the presence of the interhumerals 

 marks it off as different from all North American turtles hitherto described. Archceochelys 

 (Lydekker, Cat. Foss. Kept., pt. in, 1889, p. 219), from the Wealden of England, has the 

 humerals separated by what has been regarded as an intergular, but which is quite as likely 

 an interhumeral. Behind this come in succession an interpectoral, an interabdominal, 

 and an interfemoral. The latter extends itself backward between the anals also. That is, the 

 scutes which usually join in pairs along the median line are here separated the length of the 

 plastron by a series supposed to be azygous. These median scutes in both Polythorax and 

 Archceochelys are probably homologous with the median series of Dermochelys. 



Mr. Lydekker places his genus provisionally in the Amphichelydia. 



Genus NAOMICHELYS nov. 



A genus known only from the entoplastron. Outer surface ornamented with elevations 

 resembling small shot. A long narrow scute (intergular or interhumeral) occupies most of the 

 length of the bone. Gulars ? and humerals ? present. 



Type: Naomichelys speciosa Hay. 



The relationships of this genus are not certain. It may belong among the Pleurosternidae 

 rather than among the Baenids. It is here put in the vicinity of Polythorax. 



Naomichelys speciosa sp. nov. 



Plate 40, figs. 2, 3. 



The only portion of this species at present known is an entoplastron which was collected 

 in 1904, by Mr. Barnum Brown, of the American Museum of Natural History. It was secured 

 in the Upper Jurassic, Morrison beds, 25 miles east of Pryor, Montana. The catalog number 

 is 6136. The bone is complete, except that the extreme anterior end is broken away. The bone 

 is 85 mm. long, and was originally about 10 mm. longer. The width is 78 mm. The thickness 

 is quite uniformly close to 7 mm. Where the bone joined the epiplastra the upper surface 

 extends out a little farther than the lower. The hyoplastrals overlapt extensively the ento- 

 plastron, as may be seen from plate 42, fig. 3. Fig. 2 of the same plate shows the scutes and 

 the ornamentation of the inferior surface. Five scutes are represented in the bone. There 

 is a long median scute which narrows forward, as well as backward. It seems probable that 

 anteriorly it did not extend beyond the bone. This scute may be the intergular which was 

 crowded backward by the gulars as in Chelodina nova: guinea (Boulenger, Cat. Chelomans. 

 pi. vi), or it is possibly an interhumeral or an interpectoral. Attention is called to Cope's 

 Polythorax and Lydekker's Archceochelys. 



On each side of the scute just described is another which may be either an intergular or a 

 gular. Behind this is a large scute which is assumed to be the humeral. 



