157 



Gonocephalites. The glabella, however, does not decrease in 

 width forwards, and the fixed cheek is too broad ; neither 

 can it be placed in JDikelocephalus. On the other hand, the 

 Trilobite in question may have some relation with Loganellus, 

 Devine* ; but here again there is a discrepancy between 

 their respective facial sutures, if the line visible in the 

 Tasmanian form may be so construed. 



2. Fig. 10 represents another species (?), apparently con- 

 generic with the last, and to differ simply in the form of the 

 glabella, which is pear-shape and less robust, and proportion- 

 ately narrower. I take this to be a second species of the 

 genus to which the former Trilobite belongs. 



3. The next form to be referred to is represented by Fig. 11, 

 We observe here much the same outline and convexity of the 

 glabella, but apparently only one furrow on each side. It is 

 in a wretched state of preservation, and too much reliance 

 should not be placed on it. 



4. The last specimen (Fig. 12) is a fragmentary head shield 

 exhibiting an almost quadrate glabella, without any trace of a 

 furrow. It is short, convex, and almost square, blunt in front, 

 with the axal and neck furrows strong and deep (in casts). 

 Without committing oneself to a definite opinion, the strong 

 resemblance to Billings' genus Bathyurus may be pointed out. 



A few words may now be said as to the probable age of the 

 Caroline Creek beds, geologically speaking. In the Lower 

 Silurian Eocks of Great Britain, Conocephalites r- nges from 

 the Lower Lingula Flags to the Menevian Group, but is 

 chiefly characteristic of the former. Bikelocephalus, similarly, 

 is confined to the Lingula Flags in Britain. The genus 

 Asaphus has a wider range in time, being known as low as the 

 Tremadoc, and as high as the Llandeilo, but it may be said 

 to be representative of the Caradoc and Llandeilo. In 

 Bohemia, according to M. Barrande's tables, f Cono- 

 cephalites is found exclusively in Etage C, the equivalent of 

 our Lower Lingula Flags, whilst Asaphus possesses very much 

 the same range as in Britain. According to Miller's excellent 

 Catalogue of " American Palaeozoic Fossils," OonocephaUtes is 

 confined without exception either to the Potsdam or St. John's 

 Groups. The same authority restricts Dikelocephalus to the 

 Potsdam and Quebec Groups of the American Geologists. 

 Now, the Potsdam Group, and in part the St, John's, corre- 

 sponds in age to our Lingula Flags, and to a portion of M. 

 Barrande's Etage C. The Quebec Group is about the equiva- 

 lent of the British Arenig Series, or Lower Llandeilo. Accept- 

 ing, therefore, the determination of the foregoing Trilobite s 

 as approximating to the truth, it appears more than probable 

 that the age assigned to the fossils from the Caroline Creek 

 *See Billings, Pal. Foss., Canatla, p. 200. tSyst. Sil. Bohfime. 1. Suppl. p. 276. 



