THE GALAPAGOS TORTOISES. 277 



costal scales from the fourth to the eighth marginals, continuous with the edges 

 of the carapace in front and behind. This keel is not retained on old specimens 

 to such an extent as on T. clivosa, Plate 21. There is a weak notch on each 

 side at the fourth marginal and another at the eighth; the grooves from these 

 notches extending toward the nuchal notch and toward the caudal scale are 

 shallow but distinct. In front of the humeral notches, and behind the femoral, 

 the marginals form scallops. Anteriorly the marginals have a slight inchne 

 downward. All of the scales are strongly marked by striae. The amount of 

 prominence in the areolar spaces varies; on specimens of a length of two feet 

 or thereabout the areolars are decidedly prominent on the first and on the fourth 

 and the fifth vertebrals. The descent from the fifth is quite steep. The striae 

 persist on some; on other species they are nearly or completely lost, Plate 36 

 {T. nigra). The bones are light. On the sternum the concavity is absent or 

 shallow on the young, of moderate depth on specimens more than half grown. 

 The gular scutes are narrow and swollen above the ends which are slightly 

 turned downward below the edge at each side of a shallow notch. The anal 

 scutes are longer than wide and the pair are separated behind by a moderate 

 notch; the angle on a scute is thin, sharp, and curled upward somewhat. The 

 caudal notch persists on large specimens. Plate 8 contains the outlines of the 

 larger of Bibron's types, a forty-one inch specimen, taken from Giinther's 

 figure B of his Plate 33, apparently a 9 . Males of more than thirty inches 

 have served as types for T. wallacei, T. porteri, and T. darwini. This sex is 

 commonly the more elongate and the flanks are less full and rounded. Occa- 

 sionally the curved width is less than the curved length, as in case of the type 

 of T. darwini but in most cases the curved length and the curved width are 

 nearly equal, while the direct width is two thirds to three fourths or more of 

 the direct length. Specimens identified with this species have been collected 

 on Santa Maria (Charles), Santa Cruz (Indefatigable), Rabida (Jer\ds), San 

 Salvador (James), and on Middle and on South Isabela (Albemarle). 



The color is a uniform dark brown or black, commonly without yellow 

 markings on the lower surfaces. 



In all likelihood a note by Mitchill, 1815, was the first mention of this species. 

 The measurements he gives are impossible when appHed to any known tortoise 

 of the Galapagos, but they make their nearest approach to T. nigrita. Since 

 the article Description of the great Gallapago-Tortoise. From Dr. Mitchill's 

 Lectures on Natural History, contains interesting matter, and has been ignored 

 heretofore, it is reprinted from the Medical Repository, 2, p. 309 and 404. 



