Sedimentary Rocks. 71 



(VII.) Upper Western Kororoit Creek — ■ 

 Polyzoa, branching form. 



Crinoid, columnar, and impressions and moulds of crinoid 

 arms. 



Mr. Chapman adds : " The Fossils indicate a mid or newer 

 Silurian horizon. As a distinct horizon of grits, I should say 

 they were basal, and, from the fossils, basal Yeringian. The 

 Leptacna is of a type only found in the Newer Silurian, as also 

 the Encrinurus, and cf. Eridotrypa. The faunal elements sug- 

 gesting an older phase of the Silurian are the abundance of 

 Camaratoechia and Rhynchotrema." These identifications were 

 made at an early period of our investigation, and represent the 

 more obvious features of the fauna. Since they involved a dis- 

 tinct break between Grits and Upper Ordovician, and the field 

 evidence pointed to a close connection, a more thorough search 

 was instituted, resulting in the discovery of Diplograptus re- 

 mains in the Grits themaelves, and of Diplograptus and Climaco- 

 graptus in shales interstratified with them. These fossils are 

 rare, many hours of search resulting in the discovery of less 

 than half-a-dozen specimens, but that they are typical is shown 

 by their widespread distribution. They were found at " Dal- 

 rymple's," Lancefield Junction, Watson's Creek, and the Western 

 Kororoit. This led us to transfer to the Grit series Diplograptus 

 shales which we formerly considered distinctly Upper Ordovi- 

 cian, but which are of coarser texture, and more rubbly than the 

 normal graptolite shales, and which are closely connected with 

 grit bands. Since such shales had yielded Dicranograptus at 

 " Dalrymple's," it was of importance to determine their relation 

 to the Grits. This junction is obscured by soil, but after care- 

 ful search, we are of opinion that shales and grits are here con- 

 formable. 



We have also Messrs. Skeats and Summers' accounts of re- 

 sorted Kerrie Conglomerate pebbles in Lower Silurian mud- 

 stones at Springfield. .These mudstones are portion of a series 

 which contains grits like the Riddell Grits in texture and frag- 

 mentary fossils, but which is Silurian, Monograptus occurring 

 in shales above and below it. 



We assume, as will be shown later, that the Riddell Grit is 

 older than the Kerrie Conglomerate, and, if we adopt Messrs. 

 Skeats and Summers' theory of the origin of the Springfield 

 pebbles, then the Riddell Grit would be not later than the Lower 

 Silurian. 



