234 



BRITISH FOSSIL CRUSTACEA. 



1867, the first evidence of the existence of a true Limuloid form of Crustacean from the 

 uppermost Silurian shale of Lanarkshire. 



It is hardly possible to estimate too highly the persevering labours of Mr. Robert 

 Slimon and his sons in the investigation of these Lesmahagow deposits, and one is led to 

 reflect what an enormous amount of additional knowledge would result if other local 

 geologists devoted themselves Avith the same energy to the investigation of the rocks of 

 their own particular district. 



Unlike the majority of the Crustacea obtained from these deposits, our present 

 acquisition cannot be classed among the giants of those days, the specimen only 

 measuring five and a half lines in greatest length, and six lines in greatest breadth. It 

 is preserved upon the extreme edge of a piece of shale, so that, unfortunately, the 

 ultimate segment, as I conceive, and the telson or tail-spine are wanting through being 

 cut off by a cleavage-plane. I have allowed the artist to indicate their probable size in 

 dotted lines in the subjoined woodcut (fig. 78), the rest of the figure actually preserved 

 being given in outline. 



Cephalon. 



Thorax. 



Abdomen. 



Pig. 78. — Neolimulus falcatus, H. Woodw. Upper Silurian, Lesmahagow, Lanarkshire. 

 (Enlarged four times.) Breadth of original six lines ; length 5| lines. 



The head-shield is nearly two thirds broader than long, the front margin is semi- 

 circular and smooth, and the latero-posterior angles are acute and directed backwards. 

 The posterior border of the head is concave, curving slightly inwards near the centre, and 

 backwards towards the latero-posterior angles. 



The glabella is semicircular, and has a tolerably well-defined lateral border separating 



