134 PROF, GROOM ON THE CAMBRIAN AND [Feb. 1902, 
and paleontologically; but whether the formation is 
best regarded as the natural base of the Cambrian, or 
as a separate pre-Cambrian formation, such as the 
Etcheminian may be, the evidence appears as yet 
insufficient to show. 
IX. Conciustons. 
The Cambrian and lowest Ordovician sediments attain a con- 
siderable development in the Malverns. The maximum thickness 
may be estimated as over 5000 feet, while the minimum can 
hardly be much less than 2500 feet. To these estimates must be 
added a thickness of some 600 feet of intrusive igneous rocks. 
he series (exclusive of igneous rocks) consists of the following, 
in descending order :— 
(4) The Bronsil Shales, 1000 feet thick; grey shales containing Dictyonema 
sociale, and many Tremadoc brachiopods and trilobites. 
(5) The White-Leaved-Oak Shales; black shales including :— 
(0) The zone of Peltura scarabeoides, Spherophthalmus alatus, Ctenopyge 
pecten, Ct. bisulcata, Agnostus trisectus, etc.; thickness 500 feet. 
(a) The zone of Polyphyma Lapworthi, containing Acrotreta malvernensis, 
Kutorgina pusilla, Protospongia fenestrata, ete.; thickness not less 
than 30 feet. 
(2) The Hollybush Sandstone, comprising :— 
(0) Massive sandstones (glauconitic), probably not less than 1000 feet 
thick, and containing :—Hyolithus fistula, H. malvernensis, H, prim- 
@vus, Scolecoderma antiquissima, Kutorgina Phillipsii, etc. 
(a) Flaggy and shaly sandstones (glauconitic), not less than 75 feet 
thick, with Kutorgina Phillipsti, Scolecoderma antiquissima, Hyolithus 
sp., ete. 
(1) The Malvern Quartzite, consisting chiefly of grey quartzites and 
conglomerates, seldom slightly glauconitic; probably several hundred 
feet thick; containing Kutorgina Phillipsii, Obolella (?) Groomii, and 
Hyolithus primevus. 
The Malvern Quartzite probably at one time rested unconformably 
upon both of the Malvern series recognized as pre-Cambrian, since it 
contains angular fragments and rounded pebbles of Uriconian and 
Malvernian type, but it appears now to be separated from the older 
rocks by faults. It is to be compared with the Wrekin Quartzite, 
and probably with the greater part of the Hartshill Quartzite, and 
with quartzites which in other parts of the world immediately 
underlie the Olenellus-beds. 
The shaly basal beds of the Hollybush Sandstone possibly corre- 
spond with the Olenellus-beds, and with the zone of Paradowides 
Groom, Lapworth, in.the Comley Sandstone of Shropshire. 
The bulk of the Hollybush Sandstone probably represents the 
greater part of the Paradoxidian of other localities, and not im- 
probably corresponds with the Camp-Hill Quartzite (exclusive of the 
1G, F. Matthew, Ann. N.Y. Acad. Sci. vol. xii (1899) p. 41, & Bull. Nat. 
Hist. Soc. New Brunsw. vol. iv (1899) pp. 189, 198. 
