MERRTAM: TKIASSTC ICIITII VOSATIM A. 91 



111 the collection of the Koniglichen \aturalien-< abinet of Stuttgart there 

 is a small centrum which, as far as can he determined, agrees in all its char- 

 acters with the most anterior dorsal or cervical centra of lclillt//o*<iurnx or 

 Cymbospondylus. It is somewhat hroader than high, and apparently had two 

 lateral facets for rih articulation (fig. 61). The upper portion of the vertebra 

 is however damaged so that the complete separation of the facets cannot now 

 be proved. The upper facet was evidently continuous with the superior sur- 

 face for articulation with the neural arch. A somewhat broken cent nun, no. 

 3068, in the collection of the Polytechnikum of Zurich seems also to belong in 

 this region, as the superior articulation with the rib is continuous with the 

 articular surface for the upper arch. Part of the lateral face of the vertebra 

 was unfortunately covered with matrix. This centrum is nearly circular in 

 cross-section. The one from the Stuttgart collection has nearly the same form, 

 but is a little broader, indicating probably a, position near the posterior end of 

 the cervical region. 



There are no vertebrae available which represent the middle dorsal region, 

 unless possibly a specimen (fig. 62) figured by Fraas (1891, Taf. 3, fig. 12) 

 belongs there. This last vertebra is a very little higher than wide and seems to 

 bear a single small apophysis just above the middle. The writer has not seen 

 so small an apophysis for unicipital articulation of dorsal ribs in any ichthy- 

 osaur, but apophyses for rib articulation, of this size and similarly situated on 

 the side of the centrum, are found in the middle tail region. The width of the 

 centrum is, however, greater than is generally seen in caudal centra of Triassic 

 genera and the inferior surface seems to show no facets for chevrons. Fraas 

 considered this centrum a caudal. If it is not a caudal, it might possibly be 

 considered as an anterior dorsal in which the tubercle of a widely-forked rib 

 head rested entirely on the base of the upper arch. 



Several vertebrae differing considerably in their characters seem to repre- 

 sent the posterior portion of the dorsal region. Of these the larger number 

 are like figures 63, p. 50; and 11 5 and 115&. The first of these two specimens 

 was described by Fraas, the second is from the collection at Ziirich. The form 

 of the first centrum and the inferior position of the apophyses can probably 

 indicate no other position in the column than that near the pelvic region. The 

 inferior surface is rounded, showing no facets for hypocentra, and it is evi- 

 dently not a caudal but a posterior dorsal. Other centra including one (figs. 

 116w and 116Z>) from the collections at Ziirich, and two from the collections 

 of the Technische Hochschule of Stuttgart show a form of the centrum some- 

 what similar to those just described, but support only a single lateral apophysis. 

 There are in these specimens no distinct traces of facets for intercentra, and 

 it is not probable that they were situated far behind the pelvic region. 



The first indication seems to be that the forms of centra discussed above 



