Reviews — Prof. 0. C. Marsh's Binocerata. 



215 



from the end of tbe premaxillaries along the palate to the lower 

 margin of the foramen magnum, is nearly straight. The top of the 

 skull supports three, separate, transverse pairs of osseous elevations, 

 or horn-cores, which form its most conspicuous feature, and suggested 

 the name of the genus. The smallest of these protuberances are 

 situated near the extremity of the nasals ; two others, much larger, 

 arise from the maxillaries, in front of the orbits ; while the largest 

 are mainly on the parietals, and are supported by an enormous crest, 

 which extends from near the orbits entirely around the lateral and 

 posterior margins of the true cranium. These general characters are 

 well shown in Figure 1, which represents the skull of the type 

 specimen. 



"There are no upper incisors, but the canines in the male are 

 enormously developed, forming sharp, trenchant, decurved tusks, 

 which were each protected by a dependent process on the lower jaw. 

 The premolar and molar teeth are very small. 



"The orbit is large, and confluent with the temporal fossa. The 

 latter is of great extent posteriorly, but the zygomatic arches are 

 only moderately exj)anded. There is no post-orbital process. 



I 



Fig. 2. — Posterior, or occipital sur- 

 face of skull of Dinoceras mirabile, Marsh, 

 one-eighth nat. size, c, occipital condyle; 

 /, foramen magnum ; I, lateral crest ; 

 0, occipital crest ; p. post -tympanic pro- 

 cess ; t, crest behind temporal fossa. 



Fig. 3. — Posterior, or occipital sur- 

 face of skull of Tinoceras ingens, Marsh, 

 one-eighth natural size. (Letters the 

 same as in Fig. 2.) 



" The nasal bones are greatly elongated, being nearly half the 

 length of the entire skull. They project forward over the anterior 

 nares, and overhang the premaxillaries. They are thick and massive 

 bones, especially in front, and are united together by a nearly 

 straight suture. 



" The anterior extremity of the nasal bones, in both Dinoceras and 

 Tinoceras, is formed of an osseous projection, pointing forwai'd and 

 downward, and situated in front of and below the nasal protuber- 

 ances. Several specimens in the Yale Museum show that this 

 projection is formed of two separate ossifications, each in front of 

 its respective nasal bone. 



