No. 174" 



DESCRIPTIONS OF VEW FOSSIL TURTLES— HAY. 



319 



probable that the same formation occurs in the [gnacio quadrangle. 

 The number of the specimen in the catalogue of the ('. S. National 

 Museum is 653!). 



No part of this specimen is present, except the plastron. Of this 

 little is missing. The character which is depended on to separate the 

 genus Alamoseyms from Adocus is the restriction of the marginal 

 scutes to the peripheral bones. As these bones are wholly missing, 

 this character can not be observed. However, the plastron is so 

 closely like that of A. substricta, the type of the genus, that there can 

 be hardly a doubt that this 

 species, too, belongs to Ala- 

 mosemys. 



The individual was some- 

 what smaller than the type of 

 A. substricta, the total length 

 of the plastron being 335 

 mm., from which it is esti- 

 mated that the carapace was 

 about 445 mm. long. The 

 carapace of the type of .4. 

 substricta is 550 mm. long. 



Fig. 19 shows the form and 

 proportions of the plastron as 

 well as the form and propor- 

 tions of its various bones and 

 horny scutes. The following 

 table presents three columns 

 of measurements. In the first 

 column are certain measure- 

 ments taken from the type of 

 A. substricta; in the second 

 are corresponding measure- 

 ments taken from the plas- 

 tron here described; while in the third column are the measurements 

 of the first column reduced by 16 per cent of their value. This reduc- 

 tion is made for the following reason: The length of the anterior 

 lobe of A. annexa is made the standard of comparison and this is $4 

 mm. long. That of A. substricta is 100 mm., which reduced by Hi 

 per cent becomes 84 mm. All the other measurements of .1. substricta 

 being reduced in the same proportion, we have the figures of the third 

 column, which, on comparison with those of the second column, show 

 the agreements and differences in these measurements of the two 

 species. 



Fig. 19.- 



VLAMOSEMYS ANNEXA. XI- LOWER SURFACE 

 OF THE PLASTRON. 



