l6o THE HABITAT OF THE EURYPTERIDA 



of Siluric strata are exposed, ranging in age from questionable Wen- 

 lock, through the Ludlow and Lanarkian (Downtonian) and into the 

 volcanic series of the Lower Old Red sandstone. The eurypterids 

 are found in many more localities than in the Pentland Hills, but they 

 are never so abundant nor are so many genera and species represented. 

 There are four important Siluric areas in Lanarkshire, but in only 

 two of these have eurypterids been found, namely in (i) the Les- 

 mahagow inlier, and (2) the anticline of the Hagshaw Hills. 



(1) The Lesmahagow Inlier. This is the larger of the two anti- 

 clines and extends from a little north of Muirkirk northeast for 6 

 miles. The Greenock Water in the southwest and the Logan Water 

 in the northeast have exposed a number of excellent sections in the 

 gently dipping beds. The lowest beds exposed consist of a series of 

 blue greywackes with shale partings, the whole comprising 1300 feet 

 as seen along the southern margin of the area along the headwaters 

 of the Ponesk and Nethan. Only a few specifically unidentifiable 

 fossils have been obtained from this series which is provisionally placed 

 with the Wenlock. Immediately to the north of these beds occur 

 grey, blue and olive shales, with occasional nodular greywacke bands 

 yielding a good representation of lowest Ludlow fossils. 



The third subdivision recognized by Peach and Home constitutes 

 the so-called Ceratiocaris beds which are of particular significance 

 because of the surprising abundance in some places of several species 

 of Ceratiocaris, and because of the occurrence of the Ludlow fish, 

 Thelodus scoticus in one layer and finally because of the association 

 of eurypterid remains with both of these. At many different points 

 along the Logan Water the beds are excellently shown. In a small 

 gorge about three-quarters of a mile to the northeast of Logan 

 House the lowest of the Ceratiocaris beds dipping to the northwest 

 are succeeded by some zones of dark, fissile calcareous flaggy shales 

 which weather a rusty brown and which have yielded the following 

 fossils: 



Worm tracks 



Ceratiocaris laxa Woodw. and Jones 



Ceratiocaris longa Woodw. and Jones 



Ceratiocaris papilio Salter 



Ceratiocaris stygius Salter 



Ceratiocaris telson, like murchisoni M'Coy 



Slimonia acuminata Salter 



