KIMMERIDGIAN DINOSAURS. 555 



probably were not resumed in the caudal series. It has been fractured and somewhat 

 distorted by posthumous violence : but this has not affected the contour of the under 

 surface of the centrum (ib., fig. 3), or the vertical proportions of this element, any more 

 than in the case of the two previously described sacrals. 



In four centrums of dorsal or dorso-lumbar vertebras of Bothriospondylus stiffossus, 

 forming part of the same series transmitted from the Kimmeridge Clay of Swindon, the 

 characteristic excavations are conspicuous and with longer apertures than in the sacral 

 vertebrae, where these are interrupted by the broad articular parapophyses. No trace of 

 the latter processes are present in the trunk vertebrae of which the type is selected for the 

 subjects of Plate 03. 



The centrum is subconipressed (fig. 2) ; its sides moderately concave lengthwise 

 (fig. 1), with one end feebly convex, a, the opposite end rather more concave, b. I regard 

 the latter as the hinder one, and the trunk-vertebrae to be, as in Streptospondylus, of 

 the opisthoccelian type. The free surface of the centrum is smooth, save near the 

 articular ends, where there are low longitudinal risings and shallow channels. The 

 under surface (ib., fig. 4) is perforated by two or more small vascular (venous) canals 

 near the articular ends. 



The fore end (ib., fig. 2) has a somewhat irregular surface. The hind one, which has 

 suffered less from compression (ib., fig. 3), shows a similar coarse pitting and rising at the 

 central part of its surface, the peripheral part being smoother than that at the middle, 

 which has yielded to pressure, the large cancelli there having been crushed in. 



The bases of the neurapophyses (PI. 63, np), commencing about three lines from the 

 anterior end of the centrum, are continued to the posterior end. They have been 

 anchylosed to the centrum and broken away. Posthumous pressure has crushed this 

 specimen laterally and oblicpiely. Part of the floor of the neural canal is exposed 

 (at n, 11, fig. 5), and is continued outward, at o, where the spinal nerve has had issue. 

 The narrowness of the tract of the centrum, between the lateral excavations, /, /, giving 

 support to the coextensive parts supporting the neural arch, is a singular characteristic 

 of the present genus, and made it difficult to conceive that a mere jjlate of bone like 

 that between / and n^ in fig. 1, PL 63, would relate to the support of a neural arch. 

 It recalled the structure of that part of the vertebrae in the thoracic-abdominal region of a 

 Chelonian. What the character of such arch may have been we have yet to learn, in 

 the present species, from better preserved specimens. Not a fragment recognisable as 

 belonging to such portion of the vertebra could be found among the fossils ijcnt up from 

 the Kimmeridge locality at Swindon. 



Two rather more crushed and distorted centrums show, nevertheless, an increase of 

 transverse diameter indicative of their having come from a region of the spine near the 

 sacrum. The centrum shows the same opisthoccelian type, the same wide and deep lateral 

 excavations, undermining, as it were, the neural arch, an absence of transverse processes, 

 and the fractured bases of anchylosed neurapophyses. 



