ccelous, they may be called Camarasauridw and Amphirceliidce respec- 

 tively. 



The pubis is a stout bone with one slightly concave, thicker border, and 

 an opposite strongly convex, thinner margin. One extremity is truncate ; 

 the other presents one transversely truncate and one oblique face. The 

 femur is elongate, and presents a strong postero-external ridge or third tro- 

 chanter near the middle of the shaft. The head is not separated by a well 

 marked neck, and the great trochanter does not project beyond it. 



Thus while there is a striking resemblance to Camarasaurus in what 

 may be regarded as adaptive characters, in some important essentials the 

 two genera are very different. 



Amphicoslias altus sp. nov. 



The centrum of the dorsal vertebra of this reptile is contracted both lat- 

 erally and inferiorly, so that the margins of the articular extremities flare 

 outwards. The sides are flat, and the inferior surface but little convex in 

 the transverse direction. The pneumatic foramen is situated at the bottom 

 of a large lateral fossa which extends nearly the entire length of the superior 

 portion of the centrum. Its inferior border is sunken abruptly, while the 

 superior gradually shallows on the external surface of the base of the neu- 

 ral arch. The foramen is longer than high, in contradistinction to that of 

 the Camarasaurus supremus, where it is round or higher than long. 



The neural arch is very much elevated to the zygapophyses. It is 

 strengthened by a prominent rib, which extends from the posterior base 

 upwards and forwards to the base of the anterior zygapophysis. The sur- 

 face above and behind this is occupied by an extensive excavation whose 

 superior border is the line connecting the zygapophyses. The anterior 

 zygapophyses are separated medially by a deep notch which extends to the 

 base of the neural spine. The articular surfaces incline towards each 

 other. Just behind the anterior zygapophysis, a process extends outwards 

 and forwards whose extremity is lost in my specimen. Its posterior face 

 is excavated by the lateral fossa above described. This process is probably 

 the parapophysis which supports the rib. The diapophysis springs from 

 the line connecting the zygapophyses and extends upwards and outwards. 

 Its inferior surface is concave, or longitudinally excavated. 



The neural spine is thin, but its anterior and posterior borders are thick- 

 ened and double, the lateral rib-like edges being separated by grooves 

 which expand at the base. The posterior groove continues to a more ele- 

 vated point than the posterior. Each side of the spine is divided into two 

 shallow wide grooves by a median keel. The apex of the spine is much 

 thickened transversely, its obtuse extremity having the fore and aft and 

 transverse diameters equal. 



The pubic bone resembles that of the Camarasaurus supremus, but is 

 less robust in all its parts. It is also less extended in antero-posterior width 

 near the proximal extremity. 



The femur is remarkable for its slender form. It is a few inches longer 



