48 R. J- Anderson, 



All the other ribs are thinned at their anterior and posterior 

 margins, at the expense of their internal surfaces both in front and 

 behind. 



The thickest parts of the ribs are nearer the posterior borders 

 than the anterior except in the case of the second where the thickest 

 part is at the front. The ribs as John Hunter said are here 

 groined. 



As is well known the hollowing of the outer surface near the 

 anterior margine is very conspicuous except in the first and second. 



The thick ridge occupies the posterior part altogether except at 

 the angles. In the lower thirds, the thickening reaches farther for- 

 wards and the thicknesses of all the ribs are more nearly uniform at 

 the lower end. 



The entire depth of the thorax in this creature is 70 mm. in the 

 lines of the angles. The sum of the breadths is equal to 59 mm. 

 These measurements are skeletal. 



Myrmecophaga didactyla (Figured by Nuhn in his Anatomy 

 p. 324). The expansion resembles the condition in chelonia, „but over- 

 lap or join by squamous instead of dentale sutures." (Owen's Anatomy 

 vol. II. 398). See also — Meckel & Cuvier. 



The Armadillo. 



The Armadillo gives broad tangential diameters in the anterior 

 ten ribs but in the posterior three the tangential diameters are nearly 

 equal to the radial. A slight nodular prominence marks the angles 

 of the sixth seventh and eighth and the posterior borders of the ribs 

 from the fifth to the tenth especially the seventh exhibit a number 

 (7 in the seventh rib) of notches on the lower borders. The radial 

 diameters of the upper ribs are about 2,3 mm. The 5*^, Q^^ and 7*^ 

 ribs show a marked tubercle near the lower extremity the distance of 

 the eleventh dorsal transverse process from the first is about 100 mm. 

 The sternal ribs corresponding to the 2"'^, 3'^*, à^^ and 5*^ vertebral 

 ribs have their radial diameters greatest. The 6^^ however shows a 

 greater tangential diameter viz. 12 mm. near the anterior end. 



