[WHITRAVES] PALLISER’S CRETACEOUS FOSSILS 111 
coll., Mr. Mackay,”—contains a few valves or fragments of valves of a 
species of Ostrea, and a single valve of a shell whose generic and specific 
relations are uncertain. This valve is sixteen lines and a-half in length and 
about fourteen and a-half in breadth. It is moderately convex, but with 
a rather broad, shallow, transverse constriction a little in front of the 
mid-length, obliquely subovate in outline, a little longer than broad, and 
the extremely thin test is marked with fine radiating raised lines, about 
three in the breadth of a millimetre, which are minutely bifurcating 
anteriorly, when viewed with a lens. It is much more finely ribbed than 
the convex valve of Ostrea bella, if Conrad’s figures are correct, and 
indeed its surface markings are not at all lke those of an Ostrea. A 
fragment of a much larger specimen in the collection, from the same 
locality and apparently belonging to the same species, has essentially the 
same sculpure on the interior of the shell as the Spondylus complanatus 
of D'Orbigny, from the French Neocomien. Another specimen in the 
collection, from the same locality and possibly also belonging to the same 
species, is the No. 41 of the list of specimens on page 243 of Capt. 
Palliser’s report. It is a rough cast of the interior of one valve, about 
two inches and a-quarter in length and an inch and a-half in its greatest 
breadth. It is longitudinally subovate, but rather irregular in outline, 
its umbonal region is prominent, and its surface shows impressions of 
somewhat narrow, flexous, radiating ribs. 
INOCERAMUS VANCOUVERENSIS, Shumard. 
Inoceramus Vancouverensis, Shumard. 1858. Trans. Ac. Sc. St. Louis, vol.i., p. 123. 
Inoceramus unduloplicatus, Etheridge. 1861. In Hector’s paper, Quart. Jour. Geol. 
Soc. Lond., vol, xvii., p, 434, but not 1. undulato- 
plicatus, Roemer, 1852. 
Inoceramus mytiloides, Etheridge. 1861. Jb., p. 34, but not J. mytiloides, Mantell, 
: 1852. 
Inoceramus Vancouverensis, Whiteaves. 1879. Geol. Surv. Canada, Mesoz. Foss., 
vol. i., pt. 2, p. 170, pl. 20, figs. 4, 4a and b. 
Inoceramus Nebrascensis, var. Sagensis, Whiteaves. 1879. Jb., p. 172. (A typ. 
err. for I, Sagensis, var. Nebrascensis.) 
It is notoriously difficult to differentiate species in the genus Jno- 
ceramus, partly because the specimens usually obtained are so imperfect 
or badly preserved, and partly because they are so variable in form and 
sculpture. No less than seven species have been identified or described 
by different writers as occurring in the Cretaceous rocks of Vancouver 
and the adjacent islands, viz., /. Vancouverensis, Shumard, J. subundatus, 
Meek, and the forms referred by Etheridge to J. Crippsii of Roemer and 
Conrad, I. Texanus, Conrad, I. Nebrascensis, Owen, I. undulato-plicatus, 
Roemer, and J. mytiloides, Roemer. This number is probably too large, 

1 Paléontologie Française, Terr. Crét., vol. iii., p. 657, pl. 451, figs. 7-10. 
