NEOLIMULUS FALCATUS. 233 



or Limulus mohccanus ; or how the descendants of either of these last-named species 

 have found their way into the Gulf of Mexico, or reached the eastern coast of the United 

 States, and there constituted a locally derived race-species known under the name of 

 Limulus polyphemus. 



" One is led to think that the separation between these local races, permanent varieties, 

 secondary species (it matters not here which we designate them) must have taken place 

 at a time before the continents of the new world had acquired their present configuration, 

 and when the warm waters of the Atlantic mixed with those of the Pacific without 

 passing through the Polar Regions or Southern Ocean. Such intercommunication has 

 not, however, existed since the elevation of the Tertiary Strata, which now occupy the 

 depths of the Gulf of Darien, and which extend on the south-east as far as the Banks of 

 New Granada in the Pacific Ocean. The conclusion is that the common ancestors of the 

 American and Asiatic Limulus must have been connected before the Tertiary Period ; and 

 if we find a great hiatus between these animals and those of the Jurassic Period, the 

 remains of which are preserved in the Lithographic stone of Solenhofen, it is because the 

 marine deposits of the Cretaceous Period now accessible to our investigations contain 

 only deep-sea forms of life; whereas the King-crabs are never found save in the 

 neighbourhood of the coast. It seems probable to me that all the Limuli of the present 

 epoch are descendants of the Limulus of the Jurassic Period, and that they constitute the 

 derivative or secondary species in place of the primordial form ; in fact, that they 

 are multiple creations from one single zoological type." 



Sub-order— XIPHOSURA, Gronovan. 1764. 



Genus 1. — Neolimulus, LI. Woodward, 1868. 



Gen. Char. — Head-shield more than twice as broad as deep, glabellal portion 

 occupying more than half the entire breadth of the head, genal portion small ; ' facial 

 suture ' crossing the cheeks obliquely from the postero-lateral angle of the shield to the 

 compound eyes. Larval ocelli two (or four ?) in number. Post-cephalic segments free, 

 8 (perhaps 9 or more) in number, central axis rapidly diminishing from before backwards; 

 telson not known. 



Species 1.— NEOLIMULUS FALCATUS:— H. Woodw., 1868. PL XXXI, 



fig. 8 ; and woodcut, fig. 78, p. 234. 



Neolimulus falcatus, H. Woodw., 1868. Geol. Mag., vol. v, p. 1, pi. i, fig. 1. 

 It was with extreme interest that I obtained from Mr. Robert Slimon in September 



