FOSSIL LEPORIDAiK—PALAIOLAGUS. 375 
posterior simple column, whose section forms an odd cusp or lobe behind. 
The fourth true molar then follows, also with an odd fifth lobe behind. This 
lobed form: of the molars is so different from that of the adult as to have led 
me to describe it as indicating peculiar species under the name of Tricium 
avunculus and T. anne. 
“Tn the next stage, the fifth small molar appears in view, and the second 
permanent molar lifts its milk-predecessor out of the way. In a very short 
time, the posterior, or odd, columns entirely disappear, sinking into the shaft, 
and the permanent molars assume the form characteristic of the species. The 
Jast stage prior to maturity sees the first milk-molar shed, and the younger 
portion of the first permanent molar protruded. There is the merest trace of 
a posterior lobe at this time, and that speedily disappears. The anterior lobe 
is subconical, and is entirely surrounded with enamel. By attrition, the two 
lobes are speedily joined by an isthmus, and for a time the tooth presents an 
8-shaped section, which was supposed to be characteristic of the genus. 
Further protrusion brings to the surface the bottom of the groove of the 
inner side of the shaft, so that its section remains in adult age something 
like a B.” 
PALHZOLAGUS AGAPETILLUS Cope. 
Paleolagus agapetillus Corr, Paleont. Bull., No, 15, 1873,1; Ann. Rep. U. 8. Geol. Sury. Terr. for 187 
(1874), 478. 
Smaller than P. hayden?, but more robust, with larger incisor teeth. Molars 
all composed of two columns. Founded on a mandibular ramus, with the 
first and last permanent molars just protruding. From the Miocene deposits 
of Colorado. 
PALEOLAGUS TURGIDUS Cope. 
Paleolagus turgidus Corr, Palwont. Bull., No. 16, 1878, 4; Ann. Rep. U. S. Geol. Sury. Terr. for 1873 
(1874), 479. 
Tricium paniense Corr, Palzont. Bull., No. 16, 1873, 5. 
Larger than P. haydeni, but otherwise not much different. From the 
Miocene deposits of Colorado. 
PALMOLAGUS TRIPLEX Cope. 
Paleolagus triplex Cork, Paleont. Bull., No. 16, 1873, 4; Aun. Rep. U. 8. Geol. Sury. Terr. for 1873 
(1874), 479. 
Similar in size to P. haydeni, from which, however, Professor Cope 
regards it as distinct. From the same Miocene deposits of Colorado. Known 
only from an imperfect mandibular ramus. 
