Swanston— Silurian Rocks of Co. Down. 



FOSSIL LOCALITIES. 



TlEVESHlLLY. — About two miles south of Portaferry, and a short distance 

 east of the bridge on the main road over Carstown Burn, are several quarries 

 formerly worked for roofing- slate. The quarries are low lying, and in winter 

 aie filled with water. In dry seasons, however, the rock can be reached, and 

 proves to be thin fissile slates and flags, varying in colour from almost black to 

 pale greenish gray : the dip is nearly vertical, and they have the usual strike 

 of about N.E. and S.W. The dark bands are very fossiliferous, and many of 

 the fossils are beautifully preserved ; fifteen species have been obtained from 

 this locality, all, with the exception of one crustacean, belonging to the Grap- 

 tolitidse . 



Coalpit Bay.(i) — This locality is situated on the shore, about three- 

 quarters of a mile south of Donaghadee, and is only accessible when the tide is 

 low. As it is the best exposure of these fossil -bearing rocks, a more detailed 

 account of it is here given. 



A series of massive grey grits and slates occur to the southward of the 

 little bay, dipping at high angles to the south, and terminating northward in a 

 low escarpment. At their base we find the following rocks, upon which they 

 apparently rest conformably : — 



1. Massive black slates, with several light-coloured clay bands ; the slates 



containing, among others, the following characteristic fossils : — 



RASTRITES PEREGRINUS, var. HY- MONOGRAPTUS TENUIS, Portl. 



BRIDUS, Lapw. ,, LOBIFEROUS, M'Coy. 



MONOGRAPTUS SEDGWICKII, Portl. DlPLOGRAPTUS HUGHESII, Nich. 

 „ INTERMEDIUS, var. PROTEUS, ,, SINUATUS, Nich. 



Barr. ,, tamariscus, Nick. 



Cephalograptus (Diplograptus) cometa, Geinitz. - • 10 feet. 



2. Dark green mudstones, with several bands, each from two to four 



inches thick, of buff and light purple clays — unfossiferous — 35 feet. 



(1). So named from a futile attempt to find coals in the black Graptolitic slates here ex- 

 posed. 



