6 PROCEEDINGS OF THE ACADEMY OE 



perfectly agreeing in every respect with the 0. odorata, with the tail unguicu- 

 late, I would not hesitate to say at once, that my learned friend's division was 

 unnatural. In all species that I have seen, except those brought from Mexico 

 by Mr. Pease, the posterior lobe of the sternum is emarginate behind, and is 

 but slightly moveable ; in the Mexican species, on the contrary, it is entire and 

 capable of entirely closing up the box of the shell ; in both cases the faculty 

 arises from the peculiar formation of the joint, being either sutural or liga- 

 mentous. 



The following is the distribution according to Mr. Agassiz's system of such 

 Kinosternoids as I have had an opportunity of examining. 



KlNOSTERNUM. 



Mexicanum, integrum, triliratum. 



Thyrosternum. 



Scorpioides, leucostomum, longe caudatum, pennsylvanicum, sonoriense and 

 Henrici. 



Ozotheca. 



Odorata, guttata, hirtipes ? 



The animal, the description of which follows, was somehow omitted in 

 my monograph in vol. vii. Proc. A. N. S.; it differs remarkably from others 

 of Mr. Agassiz's genus Kinosternum, in having the upper jaw not hooked, and 

 the tail not unguiculate. 



K. triliratdm. Head and neck above spotted with yellow, the spots on the 

 cheeks larger, beneath yellowish irregularly varied with dusky, jaws yellow 

 varied with black, the upper entire, not hooked. Chin with four small warts. Fore 

 legs above dusky, beneath yellowish brown with three plicae or large scales ; 

 hind legs cinereous brown with four large scales near the heel. Tail short, 

 black, pointed, without a nail at the end. Shell regularly oval, brown, very 

 convex, strongly tricarinate on the back, very declivous on the sides, the 

 outer edge of the margin sharp and projecting, the scutae with more or less 

 concentric striae, and others radiating from behind. Vertebral scuta? elon- 

 gated, imbricate, emarginate behind, the first triangular with the apex some- 

 what truncate and the base angled, applied to the nuchal and first marginal 

 only, the second, third and fourth hexagonal, the anterior and posterior sides 

 very short, the fourth with the two lower sides much shorter than the upper, 

 the fifth triangular with the apex truncate and the base a little angled ; the 

 first lateral is four-sided, the lower side with four facets, second and third pen- 

 tagonal, fourth irregularly five-sided ; the nuchal scuta is wider at the base, 

 the rest of the marginals square and oblong, increasing in size to the extremity 

 of the shell : sternum yellow, varied with black, entire and rather poised be- 

 hind, bivalved, completely closing up the box of the shell, wings very short, 

 applied partially to the fourth and entirely to the fifth, sixth and seventh mar- 

 ginal scuta?, all the scuta? of the sternum are concentrically striate; the gular 

 large, triangular, pectorals irregularly four-sided, the anterior side curved, 

 brachials triangular with the apices truncate and the base rounded, caudals 

 right angled triangular ; inguinal scuta long, rather wide, joining the axillary. 



Length of the shell 5 inches, height 2-5, tail -8. Brought from Mexico by 

 Mr. Pease. 



I conclude by observing that Mr. Agassiz thinks my K. Mexicanum is the 

 same as Mr. Bell's K. Shavianum. The author last named supposed that he 

 possessed the identical specimen from which Dr. Shaw made his figure. 

 There can be no doubt that Dr. Shaw's figure represents my K. Mexicanum, 

 although the shell is represented without a nuchal and without caudal 

 marginals. Mr. Bell's species has the tternum narrower than the shell, 

 and emarginate behind ; it undoubtedly belongs to the scorpioides. In the 

 seventh volume of Proc. A. N. S., in my description of this species, it is 

 said that the sternum is entire ; it is really shallowly emarginate. They 



[J; 



an. 



