156 Proceedings of the Royal Society of Victoria. 



the development of spines is not remarkable. The genus 

 resembles Asaphiscus, Meek, 1873, which has, however, a conical 

 glabellum. The spiny border of the pygidium resembles that of 

 Ceraurus (syn. Chicrurus), but Notasaphus appears to be a true 

 Opisthoparian (using Beecher's classification), as the specimens 

 suggest that the genal spines were born on the free cheeks. 



Dinesus and Notasaphus both have the characters of ordo- 

 vician rather than of Cambrian trilobites. They might be 

 upper Cambrian ; but their evidence does not necessitate the 

 separation of the Dinesus ida beds from the ordovician system. 



In some shales associated with the trilobite bed are some 

 fossils resembling graptolites or algae. Mr. T. S. Hall has failed 

 to find any more definite evidence than hydrotheca of the 

 Bryograptus type, so they give us no definite evidence. In Mr. 

 Ferguson's later collection there are a few brachiopods, which 

 have been examined by Mr. F. Chapman, who has reported on 

 them, and regards them as of ordovician and probably even of 

 upper ordovician age. The strike of the fossiliferous band is 

 conformable with the strike of the overlying ordovician beds. 

 It seems to me safest, with our present knowledge, to include 

 them in the ordovician, as the lowest part of that system along 

 the Heathcote line. The beds may be shown on the Victorian 

 Survey Map as simply Dinesus beds of lower ordovician age. 



III. (D). — The Heathcotian Series. 



The last rocks of this ai-ea may be grouped together as the 

 Heathcote series. They may be divided into two main divisions : 

 the first includes some clearly altered sediments ; the second a 

 series of altered igneous rocks. 



The microscopic structure of the rocks has been carefully 

 described in Mr. Howitt's excellent memoir, to which reference 

 may be made for detailed description of most of the rocks and 

 the character of their minerals. Mr. Hosvitt has determined the 

 rocks of the acid series as aplites, granophyres and labradorite- 

 porphyrites ; and the rocks of the basic series he has identified 

 as diabase, diabase-porphyrite, enstatite-diabase-porphyrite and 

 hornblende-diorite ; and one very altered series is referred to as 

 spilite. 



