Chap. III. GENERA OF CINO STERNOIDiE. 429 



TiiYROSTERNi'M iNTKOKUM, j\i/. LcContc's Cinostcmum Integrum from Mexico (Proc. 

 Acad. Nat. Sc. Phil, 1854, p. 183). This species resembles Wagler's Cinosterniim 

 hirtipes, which belongs also to this genus. Wagler's species is founded upon a 

 single male, preserved in the MuseimT of Munich, LeConte's upon a single female 

 in liis possession. I have examined both. The rough scales in the knee joint of 

 the hind legs of Th. hirtipes are a sexual character, found in all the male Cinos- 

 ternoids, and do not by any means constitute a specific distinction. The differ- 

 ence in the outline of the front margin of the carapace and the absence of an 

 odd marginal scale in Cinosternum hirtipes may prove specific, though a tendency 

 to such difterences is already noticeable among the males and females of Th. penn- 

 sylvanicum. I have not seen Cin. Doubledayii, Grat/ ; but I doubt its specific differ- 

 ence from C. pennsylvanicum, as well as its Californian origin. Nor have I seen Cin. 

 leucostomum, Dinti. and B/7>r. ; but 1 have often noticed specimens of Cin. pennsyl- 

 vanicum with a white jaw, especially among the females, and Dumei'il and Bibron's 

 species is founded upon a female. 



III. Platythyr.\, A(/. The jaws are very weak ; the mouth is broad and short. 

 The head is long and low ; it is regularly arched, back of the eyes ; its sides 

 curve slightly between the eyes and ears ; its roof is very narrow between the 

 eyes, and, as the mouth below is broad, the eye-orbits are carried far outward 

 at their lower edges, and therefore open upward as well as forward and side- 

 wise. The skull does not rise back of the orbits ; indeed, the oi'bits project above 

 it at their upper edges. The nose is short, much shorter than in Cinosternum ; 

 its outer surface curves all round it, so that, when the fleshy parts are preserved, 

 it is rounded and pointed ; its bony roof does not pi'ojoct forward as far as the jaw 

 projects under it. The outer surface of the jaw slants inward under the eyes, curv- 

 ing out, above the alveolar edge, very little if at all ; at the front end it slants 

 backward faster than it slants inward at the sides, and the alveolar edge rises there; 

 but just at the symphysis the jaw is brought down to a small, short point. The 

 upper maxillaries are narrow from above downward, and weak. The vertical alve- 

 olar surflice is not as high as in Thyrosternum ; the horizontal alveolar sur- 

 face is broad, but the bone under it is tliiu. Tlie lower jaw is also weak, being 

 very thin, especially about the symphysis, and not high, as in Thyrosternum. 

 It is drawn out at the sj-mphysis to a slender point. The alveolar surface is 

 narrow all round ; in front it is nearly vertical, and it flattens toward the angle, 

 but near the angle the outer edge is raised somewhat more than in the other 

 genera. The outer surface of the sides curves considerably outward for a short 

 distance below the edge near the angle, and the jaws shut close. These jaws 

 are clearly not fitted to tear any strong, fibrous substance ; the only food found 

 in the intestines of a specimen examined with that view was a mass of insects. 

 The type of this genus is altogether new to science. 



