13 



apparently very short. On the lower surface, one on each side of the median line and almost 

 touching, are two poorly defined very shallow oblong depressions — (well defined and com- 

 paratively deep in one of the small centra). The sides of the centrum are slightly 

 depressed between the raised margins of the articular faces ; here the surface when preserved 

 is seen to be marked by short inosculating ridges directed antero-posteriorly. The structure 

 of the articular faces is dense ; that of the remainder, which forms the greater part of the 

 centrum, is finely cancellous. 



Measurements. 



MM. 



Type specimen, Plate I, figures 1, 2 and 3 : — 



Height of centrum '. .• 12-0 



Breadth 16 8 



Length "........ • 58 



Smaller specimen: — 



Height of centrum 9 



Breadth 110 



Length 3 ■ 8 



A basi-occipital bone that apparently belongs to this species is shown on plate I, figures 

 4, 5 and 6. Its posterior termination has the form of a vertebral centrum having a concave 

 surface for articulation with the first vertebra. The bone narrows slightly forward ; anteriorly 

 it is incomplete, but apparently only a small portion is missing. Seen from above, (fig. 4), 

 there is a deep excavation in the median line at some distance in advance of the posterior end ; 

 representing the hinder basal part of the brain cavity. Above, posteriorly, is seen the floor 

 of the foramen magnum, extending backward from the brain cavity as a narrow smooth 

 surface, on each side of which is an area indicating the probable position of occipital arches 

 such as are found in the living Amia calva, Linn. Laterally, and directed upward and 

 outward, occur concave facets for the articulation of the exoccipitals. Inferiorly, (fig. 5), the 

 bone is flatly convex transversely, with a broad median longitudinal groove that does not extend 

 backward to the border of the articulating cup. On each side of the basal surface is preserved 

 the facet for the parasphenoid which evidently in this fossil form terminated posteriorly in two 

 branches as in the living species. A caual enters the basi-occipital at the side (c, fig. 4) and 

 finds an exit from the lower surface beside a similar opening of the corresponding canal of the 

 opposite side of the bone; this pair of foramina have their position in the median line of the bone 

 between the hinder ends of the parasphenoid. The posterior articulating cup, fig. 6, cor- 

 responds in general size and contour with the type centrum of Amia exilis, its breadth being 

 considerably greater than the height. Slightly above mid-height in the cup is a minute 

 notochordal foramen. As seen from behind, the outline of the cup is rather flat in the centre 

 below, and laterally subangular. The limits of the vertebra forming the posterior end of the 

 basi-occipital, being the third of the three vertebra? that are thought to enter into the com- 

 position of this bone, are faintly indicated in the specimen. 



Lepidosteus longus, sp. nov. 



Plate I, figs. 7, 8 and 9. 



A species of Lepidosteus is represented by an opisthoccelous vertebra. A few thick, 

 smoothly enamelled, rhomboid scales, included in the collection, probably belong to the same 

 species as the vertebra. 



