200 



BRITISH FOSSIL CRUSTACEA. 



The evidence of concealed segments afforded by the dichotomising nerve-fibres of the 

 abdomen and ' telson ' in recent Limulns under dissection (see Pis. XXXIV, XXXV, 



Fig. 72. — Hemiasph limulcides, H. 

 Woodward, Lower Ludlow, Leintwar- 

 dine. 



h, the head ; th, the sixth thoracic 

 segments ; ab, the three abdominal 

 somites ; t, the telson. 



Fig. 73. — Tail-spine of Stylonurus, sp. (natural size), Lower 

 Old Red Sandstone, Forfarshire. Drawn from a specimen in the 

 Museum of the Geological Survey of Scotland. 



