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 7’. 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 incline 
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 @. Males of more than thirty inches 
have served as types for 7. wallacer, T. portert, and 7. 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 7. 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 (Jervis), 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 applied to any known tortoise 
of the Galapagos, but they make their nearest approach to JT. nigrita. Since 
the article Description of the great GALLAPAGO-TortotsE. 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. 
