BAENIDv. 67 



The vertebral scutes are relatively narrow, the second having a length of 88 mm. and a width 

 of 65 mm.; the third a length 01*85 mm - anc l a width of about 70 mm.; the fourth a length of 

 80 mm. and a width of 70 mm.; the fifth a length of 48 mm. and a width of 80 mm. In the 

 case of the first vertebral the same lack of symmetry is to be seen as has been observed in mi 

 many other specimens belonging to the genus Ba'ena. 



The costo-marginal sulci are distant from the edge of the carapace about 11 mm. Those 

 subdividing this anterior marginal region are too obscure for certain determination. There 

 are indications of one which crost this region about 15 mm. to the left of the midline. There 

 was, therefore, probably a nuchal scute 30 mm. long from side to side. Beyond this the 

 marginals increase in length and breadth. Over the bridge they rise on the sides of the 

 carapace 45 mm. 



On the plastron are distinct gulars and intergulars. The humero-pectoral sulcus crosses the 

 midline on the line joining the axillary notches. Laterally the sulcus is suddenly turned forward 

 and outward. The pectoral scutes meet along the midline for a distance of 53 mm., and extend 

 laterally about 72 mm. The abdominal scutes occupy 52 mm. of the midline; the femorals 67 

 mm. ; the anals 50 mm. As in other species of Ba'ena, the suture between the femorals and the 

 anals runs outward, then turns backward for some distance, then again outward. 



There are 4 large inframarginals. 



Baena arenosa Leidy. 

 Plate 12; plate 13, fig. 1; plate 14, figs. 1-3; text-figs. 44-51. 



Ba'ena arenosa, Leidy, Proc. Acad. Nat. Sci. Phila. 1870, p. 123; U. S. Geol. Surv. Wyoming, etc., 

 1870 (1871), p. 367; U. S. Geol. Surv. Montana, etc., 1871 (1872), p. 368; Contrib. Ext. Vert. 

 Fauna W. Terrs., 1873, pp. 161, 343, pi. xiii, figs. 1-3; ?pl. xv, figs. 1-5; pi. xvi, figs. 8, 9. Cope, 

 ?Append. LL of Ann. Report Chief of Engineers, 1875, p. 96; ?Wheeler's Surv. 100th Mend., 

 1877, p. 52, pi. xxiv, fig. 32. Baur, Proc. Acad. Nat. Sci. Phila. 1891, p. 426, fig. Hay, 

 Bibliog. and Cat. Foss. Vert. N. A., 1902, p. 437. 



Ba'ena affims, Leidy, Ann. Report U. S. Geol. Surv. Wyoming, etc., 1870 (187 1 ), p. 367. 



Ba'ena arenosa, the type of the genus Ba'ena, was based on a shell lacking only the anterior 

 lobe of the plastron and the anterior border of the carapace. This specimen is now in the 

 United States National Museum at Washington. It was figured and described at length in Dr. 

 Leidy's work of 1873. The specimen was obtained in the Bridger deposits, at the junction ot 

 the Big Sandy and Green Rivers, in southwestern Wyoming. These beds are regarded as 

 belonging to the lowermost of the Bridger formation. 



The specimen described by Leidy evidently had originally a length of close to 340 mm. and 

 a width of 288 mm. The rear of the carapace is broadly rounded. The vertebral scutes are 

 broader than long. The hinder lobe of the plastron is broad and it narrows slowly backward. 

 The width of the anterior lobe, taken from the outer ends of the humero-pectoral sulci, equals 

 half the length of the plastron behind this. Dr. Leidy states that the position of the former 

 sutures can not be detected. This is true as regards the outer surface of the bones; but on the 

 upper side of the plastron the sutures on each side of the mesoplastrals are to be observed. 

 The left mesoplastron had a width of about 25 mm. at the midline; that on the right side was 

 narrower. 



A portion of the pelvis and the sacral vertebrae and ribs of this specimen were figured by 

 Dr. Leidy. Later, Dr. Baur obtained from the matrix of the specimen additional parts of the 

 pelvis and briefly described them. While some parts are still wanting there is enough to show 

 that the ischia were united with the pubes along the midline and that the pubes extended at 

 least 35 mm. in front of their hinder border at the midline (figs. 44, 45). The upper end of 

 the ilium was expanded backward. The width of this expanded part was equal to the height, 



35 mm - 



The writer follows Dr. Leidv and Professor Cope in identifying the former's B. affinis as 

 the earlier described B. arenosa. The original description of B. affinis was exceedingly brief and 

 hesitating. It was supposed to be distinct from B. arenosa because of the presence of only 

 3 inframarginals. In Leidy's next reference to the species, he referred it to his earlier B. 

 arenosa. The type is now in the collection of the Philadelphia Academy. It was 



