On Fossil Fish-Remains from Snow Hill and 
Seymour Islands. 
By 
A. SMITH WOODWARD, 
LL. D., F. R. S., of the British Museum. 
I. Cretaceous. 
A. Selachii. 
Some large Selachian vertebral centra from the Cretaceous of Seymour Island, 
are of much interest on account of their resemblance to the vertebral centra found 
with the teeth of Ptychodjis in the English Chalk. They occur in nodules which have 
formed round them, and are shown of the natural size on Plate i, which also illustrates 
their structure. All the centra are biconcave discs of approximately circular shape, 
the largest measuring lO cm. in diameter (fig. i, i <?); and they are remarkable for 
their very short antero-posterior measurement (fig. i i c). The primitive double- 
cone of the centrum is partially flaked away in all the specimens figured, thus ex- 
posing the numerous fine radiating ridges which strengthen its convex faces (seen 
especially well in fig. i). Between the fine radiating ridges there alternate spaces, 
which are filled with matrix in the fossil; and these spaces end in a regular row of 
pores on the edge of the periphery of the centrum (seen in fig. i c). As shown by 
sections (fig. 2 a, 2 b), the centrum is solid at its thinnest part in the middle where 
the apices of the double-cone meet; but nearly all the space between its two faces 
is occupied with thin concentric lamellae. In the nomenclature of Hasse, the vertebra 
is therefore tectospondj^lic. Each lamina is pierced by numerous irregularly arranged 
pores, which are well seen on the exposed surface in fig. l c, and are shown again 
in several enlarged sections (fig. i d — f and 2 a — c). As usual, where each pedicle 
of the neural and haemal arches was attached, the centrum is pitted by a cavity, 
which is now filled by matrix but must have been occupied originally by uncalcified 
cartilage. As shown at a in fig. [ c, this cavity is comparatively small, not extending 
completely from side to side of the centrum. 
Schwedische Südpolar-Expedition iqoi — içoj. i 
