1)1' KM. \ I I \h DID. I . 



26l 



The specimen is a complete shell, extremely little damage having been done to either the 

 carapace or the plastron through loss or any part. Unfortunately, however, an extremely 

 compact clayey limestone has envelopt the shell, and this clings so closely to the bone that it 

 w.is very difficult to remove it. In addition to this, there had been deposited over considerable 

 portions of the shell scattered nodular masses of hematite, which became so thoroly 

 attacht to the bone that, in removing them, the surface of the bone was somewhat injured. 

 This condition has resulted in making it very difficult to determine the position and courses 

 of some of the sutures between the bones, and likewise the impressions between the different 

 epidermal scutes. Many of the bone sutures could be determined onlv by removing, by 

 means of hydrochloric acid, a thin layer of bone so that the matrix in the sutures projected 

 a little. The obdurate nature of the matrix which fills the shell has seemed to render it 

 inadvisable to attempt to remove it for the purpose of seeing characters found on the inside 

 of the shell. 



The specimen has been carefully studied and the various sutures and sulci have been 

 represented in the figures herewith provided. As to the bone sutures, they have been satis- 

 factorily made out and may be relied upon. Many of the epidermal sulci have been more 

 difficult to determine; but in general, it is believed that they are correctly mapt. 



3 2 4- 



FlGS. 523 and 324. Alamosemys substricta. Carapace and plastron of tvpe. Xj. 

 323. Carapace. 324. Plastron. 



The carapace (plate 39, fig. 1; text-fig. 323) is elongated, moderately elevated, decidedly 

 constricted at the inguinal notches, and with the peripherals behind these somewhat flaring. 

 A remarkable feature of the shell, shared by Adocus, is the large part of it which lies behind 

 the sutures separating the third and fourth costal plates above and that which separates the 

 hyoplastrals from the h\ poplastrals. Sixty per cent, of the length lies behind the line indicated. 

 So far as known to the writer, this is approacht onlv in Chelydra of living genera. Nearly- 

 half of the entire length lies behind the inguinal notches. 



In front. o\er the neck, there is an emargination in the border of the shell, while there are 

 some feeble serrations in the hinder border. The extreme length of the carapace, in a straight 

 line, is 550 mm. The greatest width, 380 mm., is just behind the inguinal notches; between 

 the third and fourth costals the width is yji. mm. The greatest depth of the shell is 150 mm., 

 but in life this mav have been greater. On each side of the middle line of the carapace, for 

 some distance, the shell is flat, there being no suggestion of a keel. The nuchal bone is 55 mm. 

 long in the midline; its lateral extent is 5} mm. at the anterior margin; go mm. where widest. 

 There are 7 neurals. The eighth was wholly supprest; the sixth and seventh were reduced in 

 size and crowded forward. The first is broadly oval, 57 mm. long and 32 mm. wide. The 

 second is narrowly oval, 44 mm. long and 18 mm. wide; the third, fourth, and fifth are hex- 



