AND AVES OF NORTH AMERICA. T.'j 



Measurements. 



In. 



Length (median above, ) to apex prefrontal, 5.5 



" (axial) to front of orbit, 4.15 



" " " crotaphite foramen, 2.2 



Width between extremities quadrata, 6. 2 



" " postfroutal angles, 2. 



" muzzle at point frontal, 3.32 



Length dermal scutum, 2 .3 



" cervical vertebra (to ball), 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 in the cranial sculpture and in size to 

 this species, than to Thoracosaurus neocaesariensis, I refer them at present to Holops, 



HOLOFS CORDATUS, Cope, 



Of this species I have only two cervical, two dorsal, and three lumbar vertehrae of one individual, all in a good 

 state of preservation. They present characters similar to those of H. obscurus in the cervical vertebra, and inter- 

 mediate between those of that species and the H. tenebrosus in the dorsals. While the fifth dorsal in the forrner is 

 deeper than wide in its articular cup 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 on the fourth dorsal, where in H. obscurus the cup 

 is regularly oval. The cervicals are not different from those of H. obscurus, except that the cup 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 Fig. 18. 

 by the gradual but complete lateral eversion of the latter. In the 

 types the posterior shoulder is remarkably prominent. The inferior 

 carina 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 vertebras, 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 : 



AMERI. PHILOSO. SOC. — VOL. XIV. 19 



