EPOREODON 



89 



The pattern of both series of molars is essentially the same. Anteroexternally the lobes form 

 prominent styles, laterally compressed at their outer extremities and expanded near the base of the 

 crown. 



Skeleton: The vertebral formula of Eforeodon is C 7, D 13, L 6, S 4, Ca 20 +. The cervicals 

 are nearly square. The anterior articular surfaces of the centra are slightly convex and their bodies 

 elliptical in cross section, with the greater diameter transverse. The posterior articular surfaces are 

 slightly concave, that is, the vertebras are opisthoccelous but not markedly so. A well-developed 

 ventral spine is present in Eforeodon. The neural canal is nearly circular, with a slight convexity 

 of the floor. The foramen transversarium is present. The transverse process consists of two 

 branches. The small superior branch projects backward and ends in a knobby process, while the 

 ventral branch is an osseous plate which projects downward, outward, and forward, with its free end 

 considerably thickened. The spines increase in size from third to last inclusive. All of them project 



Fie. 49. — Eforeodon socialh 

 Marsh. Seventh cervical vertebra. 

 CT. Cat. No. 13119 Y.P.M. 1/2 

 nat. size. (After Thorpe, 193 1.) 



Fig. 50. — Eforeodon socialh 

 Marsh. Atlas. CT. Cat. No. 

 13119 Y.P.M. 1/2 nat. size. 

 (After Thorpe, 1931.) 



Fie. 5 I . — Eforeodon socialis 

 Marsh. Axis. CT. Cat. No. 

 13119 Y.P.M. 1/2 nat. size. 

 (After Thorpe, 1931.) 



forward, except the seventh (Fig. 49) which is vertical. The spine of the last cervical is but little 

 longer and stouter than that of the sixth. Both do not possess the ventral transverse process, but 

 they do have a pair of small facets on the lateral borders of the posterior articular surface for the 

 heads of the first ribs. 



The atlas (Fig. 50) is oblong from a superior view. The articular cavities for the condyles of 

 the skull are deep and large, and the anterosuperior part of the arch overhangs them. The facets 

 for the axis are like those of the deer. The large, round dorsal tuberosity is heavy and terminates in 

 a sharp point located nearly over the anteromedial margin. The wings are flattened, with a heavy 

 posterior tuberosity. The ventral tubercle is a thick, short, rounded spine, projecting back under 

 the axis. The posterior articular surfaces are large and the anterior deeply situated. 



Exclusive of the dorsal spine of the axis, the larger diameter of this vertebra is anteroposterior. 

 The anterior articular surfaces are markedly convex, standing at an angle of about 30° from the 

 perpendicular. There is a well-marked ventral spine. The posterior end of the spine is consider- 

 ably thickened. The floor of the neural canal is medially divided by a ridge of bone 2.2 mm. high. 

 The odontoid process of the axis is oval, with the longer diameter transverse. The neural canal is 

 nearly square. The dorsal spine, I believe, was not prolonged so far anteriorly as in Agriochcerus 

 but was rather more like that of Merycoidodon (Fig. 51 ). 



The fourth cervical of Eporeodon is similar to that of the pig in many ways. It differs in that 

 it possesses a well-defined ventral spine, posteriorly thickened, a much longer dorsal spine in relation 

 to its other dimensions, and a differently shaped neural canal. 



The seventh cervical differs but slightly from that of Sus, except in size. The dorsal spine is 

 heavier and proportionately as long as that of the latter, while the ventral spine has become merely 

 a ridge. The anterior articular surface is convex and nearly circular. The facets on the lateral 



