BY F. RATTE, ING. DES ARTS ET MANUF.. PARIS. 1067 



The pleura?, however, although not complete, belong to a large 

 specimen, and show remarkably well preserved ornaments, including 

 some of the spines, and the spiny appendages adjacent to the long 

 spines (fig. 9). 



The representation of these specimens, therefore, was especially 

 interesting in consequence of these details, but still more, as 

 there seem to be traces of articulation between the axis and the 

 pleura?, a disputed point on which I will insist hereafter. The 

 head does not belong to the same specimen as the pleurae ; 

 the head corresponding to the same specimen as these last would 

 be exactly one-half greater ( x 1*5) in linear dimensions than 

 the one represented, and the total length of the restored specimen 

 from the front to the end of the pygidium, exclusive of the orna- 

 mental spines, would be nearly 120 mm. or about 4| inches. This 

 is the largest size quoted by Barrande (I.e., p. 713) iorA. Verneuili^ 

 while A. vesiculosa may attain to one-third more in size ( x 1'33), 

 or over 6£ inches. 



Our specimen belongs to the largest Trilobite hitherto recorded 

 from Australia ; the next largest forms I have seen, being probably 

 some species of Bronteus and Phacops from the same locality. 



This makes us more and more hopeful as to the richness of our 

 Silurian fauna. 



There are some few differences between the specimens alluded 

 to, and Barrande's figures of A. Verneuili and A. vesiculosa; they 

 are as follows : — 



1. In the head the larger tubercles or spines do not seem to 

 form nearly regular rows as in these species, a point rather 

 difficult to decide in consequenee of the bad state of the specimen. 



2. The rounded nodules which belong to the occipital ring 

 although separated from it and placed at the back of each of the 

 posterior lobes, are finely granulated without any addition of larger 

 tubercles as in the figures given by Barrande. 



3. In the thorax, the long spines which terminate the pleurae are 

 more distinctly arcuate than in the same figure of A. Verneuili. 



4. The four larger tubercles on each of the pleura? are regularly 

 disposed as in the above, but show, what is not seen in Barrande's 



