26 THE PROCEEDINGS OF THE LINNEAN SOCIETY 



rock ; then a limestone, composed of thin courses of hard 

 sab-crystalline nodales, weathering yellow, set in a blackish, 

 less pure limestone ; then alternations of shale and limestone to 

 the river. From this portion I have obtained the following 

 fossils : — Trilobites : Cheirurus (PI. VI, figs. 5, 6 and 7) ; 

 Galymene (PI. YI, fig. 4) ; Spherexochus (PI. Yl, fig. 2) ; 

 Homalonoius, Acidaspis, Gromus, and Encrinurus. Brachiopods ; 

 Pentanierus, including (especially to be remarked) P. obJongus, 

 (PI. VI, fig, 3), Ainjpa, Uhynclionellay Spirifera, Orthis, Lingula, 

 and Discina. Grasteropods ; Murchisonia, Euowplialus, and 

 Sellerophon. Conchifers ; OrtJionotus, Modiolopsisy and Ftermea. 



The Perdamerus ohlongus is confined to about the lower two 

 thirds of this division. Cheirurus becomes rare in the upper part ; 

 Oalceola is found all through. Especially remarkable is it that 

 near the top of this division are two bands of limestone of from 

 six to nine inches thick, containing fucoids. Crossing the river 

 at the bottom of a steep cliS", we have thin courses of nodules and 

 flags of limestone, often concretionary, alternating with shale, 

 which frequently shews the same concretionary structure, 

 gradually becoming more calcareous until it passes into an 

 absolute Coral Reef. 



The shale of this division is the richest of any in variety 

 of species. The lower part especially abounds in Pentameri ; 

 Atri/pa is scarcely less abundant ; Atrypa desquamata especially 

 plentiful. Spirifera and Galceola are equally characteristic of 

 this zone. Some of the Spirifers have a very sub-carboniferous 

 look and are like Spirifer glaber. Orthis elegantula, and canali- 

 culata, and a large Strophomena are only found here. The 

 StropJiomena, like most of those in the Yass Beds, has the 

 Dorsal valve convex in the manner of StropJiomena euglypha. 

 Cup corals are everywhere here. Of the wonders of the Coral 

 Reef at the top of this cliff*, what shall I say ? I have not yet 

 made out one tenth of the species. Among others there are, 

 however, Favosites Gothlandica^ F. aspera, and Heliolites Inter- 

 stinctus ; all Silurian species. 



The next division is characterised especially by the Trilobites 

 of the genera Jhonteus, Calymerie, and Spherexochus^ together 



