| OCR Text |
Show 118 showing the one- rooted character of those of the lower jaw, and the deep implantation of the incisor below the antepenultimate molar. The number of molars indicated by the ramus is five, the anterior in close contact with the single large incisor. The molars are subquadrate in section, the last a little longer than broad. The only one la which the crown is preserved exhibits a short crown, with its inferior enamel border notched on two, and oblique on two sides, and the external layer of the root swollen above it all ronnd. The snmmit of the crown is worn, and is divided subequally by a transverse, rather shallow, groove. One division of the crown exhibits two dentinal areas in transverse line, the other three small ones in a curved line. The extremity of the curved incisor is rodent- like, and regularly convex on the anterior face and entirely smooth. The posterior or grinding face is convex in cross- section. A large lower incisor of another individual is about five inches in length and one and a half in depth, without the increase of elevation of the superior or interior edge, as is seen in Ectoganus glir[ formis. This edge is obtusely rounded, and instead of being obliquely leveled to meet the masticatory surface of the extremity, is abruptly truncate, the masticating face turning off at one side of the shaft. The enamel is smooth and of equal width and convexity throughout. Measurements. If. Elevation of crown of molar .013 Length of crown of molar 015 Width of crown of molar * 013 Diameter of incisor ™ . 010 from tip .013 Length of series of five molars ^ 090 Depth of jaw at third molar 055 Thickness of jaw at third molar .035 CALAMODON NOVOMEHICANU8, Sp. 7lOV. Represented by a superior inoisoi'- tooth of a species of smaller size than either of those already described, and differing in various respects from those of the C. simplex, of which a fine specimen has been obtained since it was first described. Both anterior and posterior edges are protected by a convex band of enamel; and the triturating surface is tran verse in the direction of the depth, and oblique in that of the width. The shaft increases in depth toward the root and is longitudinally concave on one face and convex on the other. The enamel bands are most extended on the convex face, and unite on that side ronnd the triturating face and present an abrupt emargination on the middle of their convex border. The other, being formed of dentine only, is deeply worn by attrition. Measurements. M. Length of fragment 033 Depth at fracture 018 Depth at grinding face 011 " Width at grinding face .009 This species differs from the supposed C. simplex in this incisor in other respects than in the smaller size. The latter is concave on both sides, and on the lower border; the former convex on one side, and on the lower border. EsTnomrx BISULCATUS, gen. et sp. nov. Char. gen. ( I).- Incisors of two forms; the inferior subgliriform, bnt not growing from persistent pulps; the enamel covering a* long and narrow external vertical face, and terminating above the alveolus, thus distinguishing crown and root. The other form of ( f ) incisor with the apex encased in enamel, but extending much farther on the outer than the inner side; the crown compressed, not wider than the root. Molars supporting two V's with rounded apices directed ontward, the posterior soon wearing into a triangle lower than the anterior. The anterior elevated and transverse only distinguished from a triangle by a notch on the inner side. Last lower molar with this anterior transverse triangle, a diagonal ridge and a heel with raised border. The type of this genus is Ectoganus bisulcatus. Cope, and a second species is E. burmeis-terii} Cope. It differs from Ectoganus as well as from Anchippodus in the far less gliri-form character of the incisor teeth, which may be compared with the extremities of the slender fingers of Borne monkeys with narrow nails. Char, specif.- A species about the size of the Capybara is represented by the greater part of the dentition of the lower jaw, which includes representatives of both kinds of incisors already described under the characters of the genus. The rodent- like form is less typical of the genus than in the E. gliriformis in being rather shorter and furnished with a less extensive external enamel- plate. The dentinal column projects well internally, giving the tooth % regularly oval section. The incisor of the second form has the in* |
