AND AYES OF NORTH AMERICA. 



7;3 



Measurements. 



Length (median above,) to apex prefrontal, 



" (axial) to front of orbit, 



" " " orotapbite foramen, 



Width between extremities quadrata, 



" " postfrontal angles, 



" muzzle at point frontal, 

 Length dermal scutum, 



" cervical vertebra (to ball), 

 Width crotaphito foramen, 



In. 



5.5 



4.15 



2.3 



6.2 



2. 



?,.:)2 



2.3 

 1.7 



1.7 



This speoies furnishes Hie 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 llolops. 



IIOLOFS CORDATTJS, Cope, 



Of this species 1 have only two cervical, two dorsal, and three lumbar vertebra of one individual, all in a good 

 state of preservation. They present characters similar to those of .11. obscurus in the cervical vertebrae, and inter- 

 mediate between those of that species and the 11. tenebrosus in the dorsals. While the fifth dorsal in the former is 

 deeper than wide in iis articular cup and slightly quadrate, the present species presents a broadly cordate oup to the 

 fifth, narrowed below, yet considerably wider than deep ; Hie II. tenebrosus presents a. regularly round or transversely 

 oval oup in the same position, much as in. H. brevispinis. The accompanying cut exhibits the difference between 

 this speoies and the II. 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 II. obscurus, except that the cup is rather more pro- 

 longed below, or subquadrate. 



The cervical vertebra 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 conoavity between the parapophyses, and Fig. 18. 



by the gradual but complete lateral oversion 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 vertebra, from their mineralization, 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. 18, 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 oup 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, an; deeper than wide, and in others the bodies are subquadrate in section, and the transverse 

 diameter of the cup greater. Measurements are as follows : 



AME11I. PHILOSO. S00 VOL. XIV. 19 



