OCR Text |
Show 123 which form the extremities of two series of similar ones, some of which arise from the strong cingnlnm which forms part of the summit of the crown. Char.- Molar without cingulum on the ( f) outer side only; elewhere very strong and crenate, at one point rising into a stout, low tubercle. The largest tubercle is near this, on the inner summit of the crown, and is connected with the larger outer by a low, broad tubercle. A smaller one intervenes between the cingular tubercle and the smaller external. The outer tubercles low aud broad, a smaller one opposite the internal between them in the position of a cingulum. Enamel coarsely rugose. Measurements, Transverse diameter 014 Longitudinal 010 Distance between apices of inner and outer tubercles 007 Elevation of cingulum .004 Elevation of outer cusp 005 The tooth described is about the size of the posterior iuferior molar of the blaek bear, ( Ursus americanus.) PlIENACODUS 8ULCATUS, sp. nOV. Represented especially by the molar tooth corresponding to that above described under the head of P. omnivorus, in good preservation. It is a species considerably less than half the size of the one just named, and presents several important differences of structure. Of the two outer tubercles, one is very small, and there is a third adjacent to the larger, produced by the enlargement of the cingulum. As in P. omnivorus, the cingulum extends entirely round the remainder of the crown, and is tubercular on the side of the least outer tubercle. The inner tubercle is connected with the larger outer by an intermediate of elongate form, so that the series when worn down resembles the trans verse ridge of the superior molar of Syposyus, and which is separated by a groove from the cingular ridge on each side. Measurements. M. Transverse diameter 008 Longitudinal diameter 006 Distance between apices of inner and outer tubercles 004 Elevation of cingulum 002 Elevation of outer cusp . 003 Size similar to that of the corresponding tooth of a Coati. OXYJBNA LUPINA, gen. et sp, nov. Represented by a portion of the cranium, which includes the greater part of the dentition. The generic characters are, three premolars and four molars above and below: lower premolars with anterior cone and posterior cutting heel; last premolar and all the molars of the superior series with an internal heel; the last molar transverse ; first and second upper molars with an anterior cone and posterior cutting lobe ; the penultimate with two anterior acute cones, the posterior forming a sectorial edge with the posterior lobe; last superior molar trenchant. Mandibular dentition, I., 0; C, 1; P. M., 3 ; M., 3; the canine teeth directed forward and upward without intervening incisors. First premolar one- rooted; second and third consisting of an anterior elevated cone, and posterior heel, which is elevated in the middle. The first true molar is nearly similar, with the posterior tubercle sharp edged. Last two molars with an anterior elevated portion and small low heel; the former consisting of three acute tubercles, of which the largest or interior forms with the anterior a sectorial blade oblique to the axis of the mandibular bone. This genus has one less molar with double median cones than Protoiomns. It is one of the flat- clawed group, of which two forms have already been described, Mesonyx, Cope, and Syvoplotherium, Cope, which present in their dentition a nearer resemblance to the genus Hyamodon than to any other of later age. It differs from both the genera named in having only six molar teeth, and the triangular type of inferior sectorial teeth has not yet been obtained among them. The O. foreipata is the larger species ; the smallest one described by me is the Oxywna morsitans. In Stypolophus brevicalea* ratusy I find three sectorials of the form described instead of two only. Char, specif,- The posterior cutting lobes of molars 1 and 2 elevated and rather obtuse, that of molar 3 lower and more acute. Molar 2 has a well- marked anterior tubercle: molar 4 consists of an outer cutting edge and inner cone. The inner tubercle of molar 3 |