EMYDIDJE. 319 



the costal plates are alternately wide and narrower at their opposite ends, the beveled surface 

 of the upper side of the hinder lobe is narrower and the axillary scute is far from reaching the 

 fifth marginal. Other differences are noted under E. ocyrrhoe. E. arethusa is distinguish! 

 by the contracted epiplastral lip and other characters. 



E. stevensomana is distinguish! from E. septana, which it most resembles, by not having 

 the anterior lobe so much expanded, and by not having the costo-marginal sulcus so near the 

 upper edge of the peripheral bones. The form and the dimensions of the anterior marginal 

 scutes are quite different in the two species; and the pectoro-abdominal sulcus of E. steven- 

 soniana does not approach so closely at the midline the hyohypoplastral suture as it does in 

 both the specimens of E. septana in the American Museum. 



Echmatemys septaria (Cope). 

 Tcit-figs. 414-420. 



Emvs ieptaria,Cott, 6th Ann. Report U. S. Geol. Surv. Terrs., 1873, p. 625; Amer. Naturalist, xvi, 1882, 

 p. 992; Vert. Tert. Form. West, 1884, pp. 130, 139, plate xvii, figs. 9-13. HAY, Bibliog. and Cat. 

 Foss. Vert. N. A., 1902, p. 448. 



Echmatemys septaria, HAY, Bull. Amer. Mus. Nat. Hist., xxn, p. 28, fig. I. 



The type of this species is in the U. S. National Museum and consists of a tolerably com- 

 plete plastron; a portion of the central region of the carapace, including the third, fourth, and 

 fifth neurals, with portions of the second, third, and fourth left costals; and a fragment showing 

 parts of the fifth, sixth, and seventh right costals and abutting peripherals. This type was 

 collected in the beds of the Washakie basin in the badlands of South Bitter Creek, Wyoming. 



All of Professor Cope's illustrations are one-third the natural size, instead of one-fourth. 

 Fig. 12 represents the piece which includes the three neurals mentioned and the corresponding 

 costals, but the sutures bounding these bones are not shown. Moreover, the lower end of the 

 figure is the forward end of the fragment. The fragment illustrated by fig. 13 is not stated to 

 have had any connection with that of fig. 12; but the two pieces join accurately. If fig. 13 is 

 conceived as being swung around so that the end of the suture near its lower right-hand corner 

 shall coincide with the end of the fracture seen in fig. 12, at the bottom of the concave 

 border on the right-hand side, the pieces will be in their natural relation. 



The first neural bone is 42 mm. long and 23 mm. wide. The next two neurals, all whose 

 form can be determined, are hexagonal, with the broad end forward. Of these the second is 

 35 mm. long and 30 mm. wide, while the third is 40 mm. long and 27 mm. wide. The periph- 

 erals are high, the fourth and fifth rising above the edge of the shell about 42 mm. The 

 nuchal and the peripherals abutting on it have sharp free borders. The nuchal is 50 mm. long 

 and 67 mm. wide. 



The first vertebral scute is 67 mm. long and 80 mm. wide; the second 78 mm. long and 

 66 mm. wide at the point of the brackets. The nuchal scute is narrow, about 20 mm. All 

 the epidermal sulci are rather deeply imprest, but are not broad. 



The inguinal buttresses extend well up into the carapace. They reach inward about 

 40 mm. from the inner surface of the fifth costal plate. They are very thin in comparison with 

 those of E. shaughnessiana. Cope states (Ann. Rep. Hayden Surv. for 1872, p. 625) that this 

 buttress is connected with both the fifth and sixth costal plates. An examination of his type 

 shows that on the left side the union is almost entirely with the fifth costal, while the sixth only 

 just comes into contact with the buttress. On the right side the sixth takes more part in the 

 articulation. The position of this buttress probably varies somewhat in different individuals 

 of this species. In No. 6085, American Museum of Natural History, described below, it 

 comes into contact with the sixth costal. In No. 1077, American Museum of Natural His- 

 tory, the buttress rests on the middle of the fifth costal (fig. 414), and is hence far from the 

 border of the sixth; but this specimen appears to be abnormal in some other respects. There 

 are considerable differences between Cope's type and No. 1077 in the structure of the costals 

 and peripherals in the region of the inguinal notch. There is no considerable difference in the 

 widths of the costals, and the peripherals coincide pretty closely with the ends of the costals. 

 In No. 1077, American Museum of Natural History, the arrangement is as shown in fig. 414. 

 This figure shows parts of the fourth, fifth, sixth, and seventh costals and the seventh, eighth. 



