38 OUR COMMON BRITISH FOSSILS. 



a very wide distribution. The other species (Old- 

 hamia radiatd) differs from the former in having the 

 setae circularly radiated instead of being fan-shaped. 

 It is also found at Bray Point, county Wicklow, and 

 the student will there readily meet with it in the 

 strata known to all in the neighbourhood as the 

 " Periwinkle Rocks." 



Apart from the pleasure of collecting these neat 

 little fossils, the visit to Bray Head will amply 

 repay the tourist. It is one of the pleasantest seaside 

 watering-places in Ireland. The zoology of the rock- 

 pools about the Head is very rich, and the visitor 

 interested in this study and geology might profitably 

 spend a few days there. Nor would his pleasure be 

 marred by the demonstrative gaiety of the humble 

 wedding-parties which make Bray their place of 

 festivity. The village is easily reached by rail from 

 Dublin ; and is especially interesting to the geologist 

 as the locality where the " oldest British fossil " is 

 found. 



Of the many thousands of species of fossils 

 found in the rocks of Great Britain, from the most 

 ancient to the most recent, perhaps no group so 

 markedly distinguishes a formation as that popularly 

 termed Graptolites. They are peculiar to the Cam- 

 brian and Silurian systems, and have not hitherto 

 been found elsewhere ; being most abundant, however, 

 in the Lower Silurian rocks. Wherever the Lower 

 Silurian rocks have been explored, if they have been 



