Agnostus sentence example
- The genus Agnostus, which belongs to the last category, occurs abundantly in Cambrian strata and is one of the earliest forms A known.
- This would lead to the supposition that the great development of metasomatic carapace is a primitive and not a late character, were it not for the fact that Paradcxides and Atops, with an inconspicuous telsonic carapace and numerous free somites, are also Cambrian in age, the latter indeed anterior in horizon to Agnostus.
- In Paradoxides, for example, there are about twenty freely movable segments followed by a very short and small pygidium, whereas in Agnostus the freely movable segments are reduced to two and the pygidium is as large as the cephalic shield.
- Somewhat resembling Agnostus is Microdiscus, with four movable segments and a large pygidium consisting of about five fused segments, the lines of union between the latter being clearly indicated.
- The upper divisions consist of bituminous limestones, clay-slates, alum-slate, and contain numerous species of trilobites of the genera Paradoxides, Conocoryphe, Agnostus, Sphaerophthalmus, Peltura, &c. The Ordovician formation occurs in two distinct facies - the one shaley and containing graptolites; the other calcareous, with brachiopods, trilobites, &c. The most constant of the calcareous divisions is the Orthoceras limestone, a red or grey limestone with Megalaspis and Orthoceras.Advertisement
- Cambrian rocks have not yet been discovered in New South Wales; but Pittman has recorded an Agnostus from Mandurama, near Orange.