How is the Cambrian divided 2 481 
Of these three extend upward to the higher zone, leaving 
only Olenus as peculiar to this fauna. 
In the fourth fauna (Dolgelly group) are the following 
genera: 
*Euloma. PELTURA. 
* Parabolina Spherophthalmus. 
* Parabolinella (?) Ctenopyge. 
* Conocephalites * Agnostus, 
Five of these genera extend upward into the next zone. 
The Conocephalites have been called Dicellocephali, but they 
are not the typical forms of Dicellocephalus with spined 
pygidium, which occur higher; they are related to Conoce- 
phalites (sens. strict) and Conocephalina, } which has short 
spines found by Brégger in the Paradoxides zone. The genus 
isnot reported from the equivalent beds in Sweden, where 
the genera of the second column held possession, but it is 
found in the fauna of Hof in Bavaria. 
The fifth Cambrian fauna (Tremadoc group) exhibits the 
following genera: 
Psilocephalus ° Euloma. 
Asaphus °Parabolina. (?) 
Cheirurus. °Parabolinella. (?) 
° Angelina. ° Dicellocephalus. 
Nesuretus. Conophrys. 
Niobe. Ampysx. 
Ogygia. ° Agnostus. 
Dionide. 
In this assemblage of fourteen genera only six represent 
“Cambrian forms” of trilobites, but in the lower half of the 
first column are a number of genera which, once thought to 
have appeared first at this period, are now found to be present 
in the West of America by representative forms at a lower 
horizon, Hence these, although hitherto regarded as Ordovi- 
cian, as already remarked, are essentially Cambrian types. 
It will be observed that in the Welsh area the four Cam- 
brian faunas, which have trilobites, show a correspondence 
{Om paradoxidesskifrene ved Krekling. 
