from Western Australia, 



439 



species has the primary ribs proportionately nearer together, and 

 the secondary ribs proportionately finer. Its primary and secondary 

 ribs are straighter than in Ammonites uralensis, d'Orbigny/ and cross 

 the periphery without interruption. 



I;ocaZ%.— Champion Bay, Western Australia. 



Of the fossils referred to in the foregoing descriptions the 

 Belemnites, Nautilus, and Ammonites (Dorsetensia) are preserved 

 in a yellowish limestone, the Ammonites {Stephanoceras) sp. and 

 Ammonites {Ferisphinctes) rohiginosus in a highly ferruginous matrix, 

 and the rest in a red or red and yellow limestone, but the specimens 

 are not accompanied by any notes on the sequence of the beds 

 from which they were obtained. The Mesozoic rocks, however, 

 in the portion of Western Australia whence the fossils were derived, 

 have been described by Mr. H. Y. L. Brown in his "Keport on 

 a Geological Exploration of that portion of the Colony of Western 

 Australia lying southward of the Murchison Eiver and westward 

 of Esperance Bay." Eeferring to the rocks of the "Mesozoic or 

 Secondary Epoch— Oolitic Period," Mr. Brown says: "The character 

 of the strata belonging to this period may be described as follows : 

 Beds of highly ferruginous clay, stone, or shale, sandstones, grits, 

 conglomerates, clays, and limestone, placed in horizontal layers 

 upon the older rocks, which originally they must have almost 

 entirely covered, but have since been cut into and denuded to a 

 great extent from off them, in such manner as to leave tablelands, 

 isolated table hills, and peaks with steep escarpments and slopes. 

 Their average elevation is about 600 feet above sea-level. _ Ihe 

 surface of this formation is generally coated with a deposit of 

 sand, arising from the weathering of the sandstones, the larger 

 areas' beino- known by the name of sand plains. There are two 

 principal areas occupied by this formation. The first, which varies 

 in width from 10 to 30 miles, extends from the neighbourhood 

 of Gingin and Yatheroo to the Murchison, and probably a long 

 distance farther northward, in a line more or less parallel to the 

 coast. Proceeding eastward it thins out, and only exists there as 

 outliers and cappings on the hills. Its average thickness, where 

 best developed, is some 400 feet. The second area commences near 

 Cape Eiche, and stretches in a north-east direction beyond the 

 Phillips Eiver, thinning out eastward to mere cappings on the hills. 

 "The uppermost beds in the first-named area are generally more 

 ferruginous than the lower, and consist of highly ferruginous 

 concretionary claystone, shale, and grit. 



... .;j 5;j o o ^;j 4S » «s 



" The great denudation which has operated since the close of this 

 period has removed a great portion of the rocks, leaving the 

 remainder as undulating plateaux and flat-topped hills, at the bases of 

 which the older rocks outcrop. As a rule these strata are horizontal, 

 although in some cases a slight undulating dip is perceptible. The 

 interstratified beds of white, yellow, and sometimes ferruginous 



1 D'Orbigny, ibid. p. 429, pi. xxxii. figs. 6-10. 



