Page:Synopsis of the Exinct Batrachia and Reptilia of North America. Part 1..pdf/79

 AND AYES OF NORTH AMERICA. Measurements. fa. Length (median above, ) to apex prefrontal, " (axial) to front of orbit, 4C It t t crotaphite foramen, 5.5 9. 2, Width between extremities quadrata, et " postfrontal angles, it muzzle at point frontal, 6.2 2, 3.32 Length dermal scutum, t cervical vertebra (to ball), 2.3 1.7 'Width crotaphite foramen, 1.7 This species furnishes the generic characters. I have not been able to ascertain the non-existence of the pre-frontal foramen in the following species, but as they bear more resemblance iu the cranial sculpture and in size to this species, than to Thoracosaurus neocaesariensis, I refer them at present to Holops. HOLOPS CORDATITS, Cop& Of this species I have only two cervical, two dorsal, and three lumbar vertebrae of one individual, all in a good state of preservation. They present characters similar to those of H. obscurus in the cervical vertebree, and inter-mediate between those of that species and the H. tenebrosus in the dorsals. While the fifth dorsal in the former is deeper than wide in its artieular eup and slightly quadrate, the present species presents a broadly cordate cup to the fifth, narrowed below, yet considerably wider than deep ; the H. tenebrosus presents a regularly round or transversely oval Cup in the same position, much as in H. brevispinis. The accompanying cut exhibits the difference between this species and the H. tenebrosus. The cordate form is distinct ou the fourth dorsal, where in H. obscurus the eup is regularly oval. The cen'ieals are not different from those of H. obscurus, except that the eup is rather more pro-longed below, or subquadrate. The cervical vertebrae referred to this species may be known by the outlines of the anterior extremity outside the cup, of which the latter partakes, which is between quadrate and cor-date ; by the distinct inferior concavity between the parapophyses, and by the gradual but complete lateral eversion of the latter. In the types the posterior shoulder is remarkably prominent. The inferior °mina is little marked on the fourth, while the hypapophyses are small and united. In a fifth, judging from the more posterior position of the parapophysis, it is formed of two partly confluent subacute. elevations. The dorsal vertebrae, from their nimeralization, condition, and time and place of discovery, probably belong to the same animal as the cervicals above described. The breadth of the cup of the fifth is a little greater than the length to the posterior shoulder, it differs from Leidy's figure of the sixth of tenebrosus, T. III., f. 13, in its large hypapophysis, which stands on nearly the entire centrum, and is very prominent, and concave in front ; the sides of the centrum are concave from cup to shoulder. In the third dorsal but a narrow space exists behind and before the hypapophysis. and the vertical diameter of the cup is less than the transverse, and exhibits the same cordate outline. As usual some (the anterior) lumbars are deeper than wide, and in others the bodies are subquadrate in section, and the transverse diameter of the cup greater. Measurements are as follows : Fig. 18. AMERI. PHILOSO. SOC.-VOL. xiv. 19