102 



THE EXTINCT BATRACHIA, REPTILIA 



surfaces for chevron bones were much narrowed anterior to the middle of series, so that we can infer that the tail 

 was proximally cylindrical. Zygapophyses turned upward, not outward. 



The portions of the three sacrals preserved indicate that the centrum is very much compressed, as in other Dino- 

 sauria. The proximal caudals, or those with diapophyses, have also compressed centra, though this is less marked 

 than in the sacrals. The diapophyses come off from the neural arch above its union with the centrum in four such 

 vertebras preserved. In these the arch is not coossifled. In the remaining nine there is no trace of diapophysis 

 beyond a ridge visible in the anterior ones, and the arches are coiissified. In the four anterior there is on the poste- 

 rior half of the median line below, a strong groove ; in the two median, a foramen penetrates the centrum ; in the 

 posterior the groove is less posterior in its position. In the posterior series of ten it is represented by an indistinct 

 plane. These vertebrae are relatively less compressed than the first, but have a more concave inferior outline. The 

 neural spines of these have been apparently curved upwards and backwards, judging from the direction of the lines 

 of ossiflc growth, as in Poecilopleurum. They originate a little anterior to the middle of the length of the vertebra. 

 Anterior to this point the, neural canal Is only partially roofed over, there being an opening into it just in front of the 

 base of the neural arch. Anteriorly the roof would appear to be composed by the union of two horizontal lamina' of 

 the anterior zygapophyses. The articular faces lor chevron hones are small. 



Dimensions of an anterior caudal; length centrum, 



depth do. from suture of neural arch, 



width articular face (anterior), 

 " centrum at middle, 

 Length of median caudal, 

 Breadth centrum, 

 Length base neural spine, 

 Length of a, distal caudal (with neural canal), 

 Diameter centrum transverse, 



" " vertical, 



Proximal caudal (with short diapophysis) length, 

 Depth centrum, 

 Width 



Three separate vertebra appear to be most probably sacrals, and indicate thai, this individual was not adult,. 

 Their form is much compressed, and the articular surfaces arc; rather expanded and concave. The superficial 

 layer of the latter is very thin, and covered with delicate raised stria', mostly transverse in direction. They present 

 the appearance of incomplete development, and would no doubt at a, later period coiissify with those of the adjaoent 

 vertebr:e, forming tin! long sacrum common to the order. Their exterior dense walls are remarkably thin, and the 

 internal structure of the centra, is coarsely spongy or almost cavernous, being far less close, and compact than that of 

 the cancellous centra of the caudals. The largest of these has a, strong median groove above, probably that of the 

 neural canal: greatest elevation of articular surface 5 in. 2 lin., greatest width of same 4 in. 3 lin. The tissue of this 

 cent rum is so coarse as to resemble the borings of Teredo. In another a large, foramen marks I he mouth of a, canal 

 which enters the centrum just behind one of the articular surfaces, and above the thickest portion oC the centrum. 

 It descends obliquely towards the middle of the centrum, but its course can be traced only an inch. Foramen .!) inch 

 in diameter. 



The number of caudals preserved is fourteen. From interruptions in the series I imagine that ten have been 

 lost, probably a lew more; I think the whole number can be estimated at twenty-dive. Both distals and proximals 

 are preserved; the former are small and slender, the latter compressed, similar to the sacrals, and with diapophysis, 

 and neural arch not coiissificd. 



This furnishes a remarkable contrast to Hidrosaurus, to which Leidy reckons fifty vertebra, and a, depth of 

 tail of a foot and a half. 



In. 



Lin. 



4. 



3 



4.1 







11. 



(i 



2.56 







4.625 





2.375 





8.25 





2.875 





1 . 1 25 





.875 





4.5 





3.125 





3. 





•They thus reiemble in several ways, the bone referred by Mantel! and Owen to the place of tin- oh quadratum, with doubt. There is little probability 

 to my mind, of this reference proving other than erroneous; see the flg. in PI. XT at the end of the volume. 



