Geology and Natural Llistory. 323 
fore be said to equal in size the largest species of the genus Prery- 
gotus, which, no doubt, attained a length of at least five feet.” 
€ specimen of Slimonia, figured natural size on plate xvii, is 
Will give in a condensed form the diagnostic characters of each 
Senus of the Merostomata. 
1. Notice of a new species of Trnoceras; by O. C. Marsu.—A 
Second species of Zinoceras, considerably larger than Z: anceps, 
is represented in the Yale Museum by portions of a skull 
and teeth, with parts of the same skeleton ; and likewise by frag- 
mentary remains of several other individuals, all from the Eocene 
deposits of Wyoming. The skull is proportionally very small, 
and indicates one of the most remarkable animals yet discovered. 
It rs apie a pair of short horns, and has also two powerful tusks, 
Which in size, shape, and direction resemble the canines of the 
Walrus, The molar teeth are small, the last of the upper series 
being much the largest. The horn cores are short, somewhat 
curved, with obtuse compressed summits. They are about 130™™* 
mM length. There are apparently but five teeth in the upper molar 
Series, and a long hiatus in front of the premolars. The tusks are 
May be called Tinoceride. : 
_ 8. Microscopical: A Life Slide—The accompanying engrav- 
Mgs represent front and side views of a form of life slide for the 
