---------------------------------+---------+----------+-------- | M. | M. | M. |T. No. 1.|T. No. 2. | Lemur. ---------------------------------+---------+----------+-------- Length of entire molar series | ·038 | ···· | ·032 Length of premolar series | ·017 | ···· | ·0125 Length of true molar series | ·021 | ···· | ·0195 Fore-and-aft diameter of canine | ·003 | ·005 | ·0065 Length of last molar[2] | ·008 | ···· | ·005 Width of last molar | ·004 | ···· | ·003 Length of second molar | ·007 | ·007 | ·0072 Width of second molar | ·005 | ·006 | ·005 Length of last premolar | ·0055 | ···· | ·007 Length of penultimate premolar | ·004 | ···· | ·005 Depth of jaw at second molar | ·012 | ·012 | ·0095 Thickness of jaw at second molar | ·0065 | ·009 | ·004 ---------------------------------+---------+----------+-------- [Footnote 2: In measurements of teeth we use the word _length_ to mean antero-posterior diameter, and _width_ to mean transverse diameter.] Specimen No. 1 was found at Cottonwood Creek, and specimen No, 2 at Henry's Fork, Wyoming. HYOPSODUS, Leidy. Pr. Ac. Nat. Sc., 1870, p. 110. Lower teeth: I. 3, C. 1, Pm. 4, M. 3, in uninterrupted succession. Last molar has cusps in opposing pairs; the antero-internal cusp on all the molars is single; the last molar has a heel, and the last premolar has an inner cusp. The true molar cusps are all high and simple. Hyopsodus paulus, Leidy. Loc. cit., p. 110. This is one of the most common fossils found in the Bridger Basin. We have numerous specimens, chiefly from Henry's Fork, exhibiting a large range of individual and sexual variation. As Dr. Leidy has already pointed out, the strength and depth of the lower jaw is extremely variable, increasing with the age of the animal; so that the most worn teeth are associated with the deepest jaws. In addition to the jaws and teeth, (which have been very accurately described), we have a portion of a pelvis and femur, which are important as tending to confirm the reference of this genus to the Lemurs.