12 Bolton, Palceontology of the Manx Slates. 



Impression of Body and Pygidium. 



"Thorax of six rings; axis convex and of uniform width; 

 body rings narrow and well marked off from one another. 

 Pleurae very broad, twice the width of the axis ; grooves deep, 

 broadening towards the extremities, and disappearing a short 

 distance from the axis ; extremities directed backwards. 

 Pygidium a little more than half the length of the thorax; 

 width double the length ; axis flattened, convex, and ending 

 bluntly in the middle of the pygidium. 



" Observations. — From the presence of six thoracic rings, 

 grooved pleura, and semi-circular smooth pygidium with feeble 

 axis ; the writer was inclined to class the specimen as an 

 ^glina, but Dr. Henry Woodward has kindly pointed out that 

 it differs from ^glina in the sides of the axis being parallel 

 along their whole length, and in being convex, whereas in the 

 former the axis diminishes in breadth from before backwards, 

 and is flattened. 



" From a careful comparison of the specimen with others 

 from the Cambrian of North Wales, Dr. Woodward is of opinion 

 that it might with equal propriety be placed in the genus 

 Asaphus as y^glina. Unfortunately the specimen is too 

 distorted and fragmentary to settle the point." 



Brachiopods are not known with certainty, for 

 though the oval depressions described as footprints by 

 Grindley and Taylor were afterwards doubtfully referred 

 to as the casts and trails of bivalves and the impressions 

 of Linguta, neither figures, specimens, nor facts which can 

 be verified, are available to justify their retention. 



The figures and description of the supposed Lingulella 

 davisii published by Binney might serve equally well as 

 figures and description of nodule masses still ifi situ in 

 the slates, and wholly inorganic in origin. 



The casts and trails of Grindley and Taylor can be 

 similarly duplicated by hollows left by the weathering out 

 of nodules, and by worm-tracks. 



If we summarise the foregoing, it will appear that a 



