has added to the Museum's
collections (No. 23230). The identity of No. 23230 is established as _A.
mutica_ by the absence of spines (see fig. 3) and by a number of cranial
characters. The specimen of _A. spinifera_ (No. 23026) is without
locality data; its identification is verified by the presence of spines
on the front of the carapace.

In the specimen of _A. mutica_ (see figures) the hump forms a smooth,
high curve, closely resembling the condition in Gressitt's specimens of
_A. steindachneri_ (_op. cit._: fig. 1). In the other two the hump is
lower and its apex forms a relatively sharp angle; in the specimen of
_A. spinifera_ the posterior face of the hump is more nearly vertical
than the anterior face. In _A. emoryi_ the rear edge of the apex is
sharply inclined (at an angle of about 45 deg.), whereas the remainder of
the surface slants at an angle of about 35 deg.

In the accompanying table of measurements of specimens in the University
of Kansas Museum of Natural History the height is measured from the end
of the rib opposite the highest elevation to the crest of the elevation,
by projected lines. The length is measured from the anterior border of
the nuchal plate to the posterior edge of the last costal plate. The
width is measured from tip to tip of the longest ribs. Catalogue
numbers of the specimens, with indication of the localities of capture
are as follows: Nos. 2215-9, 2803, 2824, 2837, Phoenix, Maricopa Co.,
Arizona; Nos. 19459-60, Ozark, Franklin Co., Arkansas; Nos. 2225-9,
Lewisville, Lafayette Co., Arkansas; Nos. 1867-70, 1874-6, 1879, 1881,
1930-1, 2666, 2761-2, 2826, 2838-42, Devalls Bluff, Prairie Co.,
Arkansas; No. 16528, Orange Co., Florida; Nos. 1872, 1878, 1943, 1964,
Doniphan Lake, Doniphan Co., Kansas; No. 2220, Douglas Co., Kansas; No.
23230, Kansas River, Douglas Co., Kansas; No. 18159, Harper Co., Kansas;
No. 2757, Smoky Hill River, Trego Co., Kansas; No. 23026, no data.

The three abnormal specimens vary in width/height ratio from 1.83 to
3.14. In the 37 normal turtles measured, the corresponding ratio is 4.64
to 7.85. The ratio of 4.64 is possibly subject to correction since the
shell tends to warp in some specimens, especially in those retaining the
skin about the periphery of the shell. The warping does not produce a
marked convexity in transverse section, but does so in longitudinal
section. Accordingly the height as here measured is little effected, and
the comparison with width ra