Distribution of the Rhabdophora. 51 



Girvan. — In the Girvan district, the Penkill group, which 

 is the representative of the Valentian or Llandovery of Wales, 

 is composed of the three well-marked consecutive subdivisions 

 of the Mulloch-Hill beds, Saugh-Hill beds, and Penkill beds. 



The Mulloch-Hill beds consist of a mass of highly fossili- 

 ferous sandstones and shales, with a coarse conglomerate at 

 the base. Brachiopods are especially abundant ; but Grapto- 

 lites are excessively rare. The only forms I have collected 

 are 



Climacograptus norinalis, Lapw. Monograptus tenuis, Portl. 



Diplograptus acuminatus, Nich. 



The Saugh-Hill beds consist of flagstones and grits with 

 coarse conglomerates and thick zones of grey shales, locally 

 crowded with well-preserved Rhabdophora. Pentamerus 

 occurs in millions in the conglomerates and limestones, while 

 the shales of the group on both sides of the Girvan Water are 

 crowded with the following Birkhill Graptolites : — 



Diplograptus modestus, Lapw. Monograptus intermedins, Carr. 



Hugbesi, Nich. gregarius, Lapw. 



tamariscus, Nich. lobiferus, M-Coy. 



folium, His. attenuates, Hoph. 



Climacograptus normalis, Lapw. leptotheca, Lapiv. 



Retiolites perlatus, Nich. tenuis, Portl. 



Rastrites peregrinus, Barr. Hisingeri, Carr. 



Monograptus Sedgwicki, Portl. fimbriatus, Nich. 



cyphus, Lapw. Salteri, Geinitz. 



The highest division, or Penkill beds proper, includes the 

 representatives of the Gala and Tarannon groups. The lowest 

 beds {the Crossopodia- Shales) consist of purple and green 

 mudstone with a few Graptolites, principally 



Monograptus galaensis, Lapw. Monograptus runcinatus, Lapw. 



Halli, Barr. Sedgwicki, Portl. 



exiguus, Nich. spiralis, Geinitz. 



Hisingeri, Carr. Diplograptus palmeus, Barr. 



The highest beds (Priodon Flags and Grits) afford 



Monograptus galaensis, Lapw. Monograptus priodon, Bronn. 



Halli, Barr. concinnus, Lapw. 



Hisingeri, Carr. Cyrtograptns Grayre, Lapw. 



Sedgwicki, Portl. Retiolites Geinitzianus, Barr. 



Ireland. — The only Irish Graptolite-bearing rocks of Llan- 

 dovery age as yet carefully studied are the Silurian rocks of 

 County Down. From the Coal-jnt Bag beds that follow the 

 equivalents of the Hartfell shales on the shores of Belfast 

 Lough Mr. Swanston* has collected the following Birkhill 

 species : — 



* Swanston, Trans. Belfast Nat.-Hist. Field-Club, Appendix, 1870-77. 



4* 



