'32 



FOSSIL TURTLES OF NORTH AMERICA. 



Osteopygis gibbi Wieland. 

 Plate it>, fig. i; plate 27, figs. I, 2; text-figs. 142-146. 

 Osteopygis gibbi, Wieland, Anier. Jour. Sci. (4), XVII, 1904, p. 118, plates v-viii and text-figs. 3-7. 



The type of this species is No. 783 of the Marsh collection of Yale University. It was 

 obtained from the upper bed of Cretaceous greensand, at Barnesboro, Gloucester County, 

 New Jersey, in 1870. It was originally studied by Dr. George Baur (Zool. Anzeiger, mi, 

 1889, p. 42), who determined from it that Cope had been in error when he stated that the 

 genus Osteopygis possest 10 pairs of costal plates. Fig. 1. plate 26, is reproduced from a 



drawing prepared under Baur's direc- 

 tions and shows the nuchal, the periph- 

 erals, and the pygal as seen from below. 

 In 1904 the specimen was full)' prepared 

 and the parts put together under the 

 direction of Dr. Wieland. A number of 

 the figures made by Dr. W 7 ieland are 

 here reproduced. 



The specimen is the most complete 

 that is known of anyspeciesof thefamilv 

 and it serves to give us a clear idea of 

 the form and the constituents of the 

 shell. It will be observed that the out- 

 line of the carapace as restored by Dr. 

 Baur (plate 26, fig. 1) differs from that 

 as restored by Wieland (text-fig. 142!. 

 Since, however, Dr. W 7 ieland fitted the 

 costals to one another and to the periph- 

 erals, and brought the plastron into 

 relation with the carapace, which Baur 

 did not do, it is quite certain that the 

 later restoration is the more accurate 

 one. It can hardly be wrong except in 

 small details. Fig. 143 shows the shell 

 from the side. 



In form the carapace is elongated 

 oval, rounded in front and somewhat 

 pointed behind. It is somewhat deprest 

 and especially the hinder peripherals look 

 more upward than outward. The length 

 in a straight line is given as 690mm.; the 

 extreme width, as about 580 mm. The nuchal bone is 127 mm. wide in front and has a maximum 

 width ol 145 mm. Its length is 75 mm. The dimensions of the neural bones are shown in the table. 

 I he eighth neural is apparently followed by a small first suprapvgal. This is succeeded 

 b) an irregularly shaped second suprapvgal, 60 mm. long and 162 mm. wide. Behind this 

 comes the posterior suprapvgal, which has a length of 60 mm. and a width of 97 mm. 



All the peripherals are suturally articulated with the contiguous ends of costal bones, except 

 tin eleventh, which articulates with the suprapygals The peripherals, except the first, second. 



In.. 142. Osteopygis gibbi. Carapace of type. 



X*. 



c.s. I, first costal bone; m. s. 12, twelfth marginal scute; n. I, 

 first neural; n. 8, eighth neural; nu.p, nuchal bone; nu. s, nuchal 

 scute; py, pygal; tpy-i, spy.i, spy- It suprapygals. 



Fig. 143. Osteopygis gibbi. Shell from left side. Xj. 



