EXTINCT BATEACHIA. 385 



visible display centra characteristic of the genus; their terminal con- 

 cavities conic, with apices meeting in the centrum; medially. The di- 

 late hfemal spines are a little more than three times as broad distally 

 as they are long, while the neural spines are a little narrower. The 

 hsemal spines stand about the middle of the centrum. The basal half is 

 furnished with an anterior ala, which leaves the anterior margin rather 

 abruptly and extends to the next spine in advance. It returns grad- 

 ually to the centrum, and is separated from the articular face of the lat- 

 ter by a notch. A similar ala exists on the posterior margin of the 

 haemal spine, which extends for a shorter distance above the base, and is 

 narrower than the anterior. Each spine presents a median groove on its 

 surface, which extends half way to the base or further ; on each side of • 

 this are some three other grooves which extend but a short distance ; 

 surface otherwise smooth. The ends of the grooves slightly notch the 

 truncated end of the spine. 



The neural spines are on the posterior portions of the centra, and not 

 in contact with the bases of those adjacent. They are without the dila- 

 tations of the hsemal spines, and are directed rather more obliquely back- 

 wards. They are similarly grooved, though without that so distinctly 

 median seen in the haemal series. 



Both neural and haemal spines become stronger towards the anterior 

 part of the vertebral column. There appear to be no zygapophyses, nor 

 diapophyses, nor rudiments of ribs. The centra are rather stout and; 

 somewhat constricted medially. There are no traces of dermal armature 

 of any kind. 



Length of a posterior centrum, 1.2 lines ; depth of a posterior centrum, 

 1.0; length of haemal spine of adjoining vertebra, 4.4; basal width, 1.4; 

 median width, 0.9; distal width, 1.1; length of a more anterior haemal 

 spine, 4.3; distal width of a more anterior haemal spine, 1.5.; length of 

 anterior neural spine, 4.0; width of anterior neural spine, 1.4. , 



In the specimen exhibiting the series from the hind limb to the ex- 

 tremity of the tail sixty-four vertebiae may be counted. The spines are 

 similar in form to those just described. Distally the sides become more- 

 parallel, at first narrowing them, but near the tip they are short, and 

 are wanting on the last vertebra. The centra support neural arches 

 well interlocked by a double articulation. Thus the anterior zygapoph- 

 ysis, as usual, looks upwards, but the posterior, which rests on it, is in. 

 connection above with a zygasphenlike prolongation of the neural arch- 

 of the following vertebra. Thus the posterior zygapophysis fills a notch. 



The posterior limb in this specimen is represented chiefly by metatar- 

 sals and phalanges, chiefly of one digit. There are in the latter four in. 

 25 



