ENTOMOSTKACA. 



365 



first six legs performing the FIG. 495. 



functions of jaws ! 



The embryonic stages 

 (Figs. 494, 495, 497) of 

 Limulus so beautifully re- 

 presented by Dr. A. S. 

 Packard, Jr.*, together 

 with the adult forms, sug- 

 gest the close relationship 

 of the Horse -shoe Crabs 



. , rn ._,. Another view of Horse-shoe Crab just 



With iRILOBATA (JPlgg. 438, before hatching-magnified. 



499), the well-known fossil forms of the Silurian, Devo- 

 nian, and Carboniferous rocks. And not far removed 

 from the Merostomata and Trilobata are the extinct Euryp- 



FIG. 496. 



Horse-shoe Crab soon after hatching 



natural size and magnified. 

 Horse-shoe Crab, Limulus polyphemus, adult. Keduced in size. 



terida, which, like the Trilobites, belong to the Palaeozoic 

 days of geology. 



* See Dr. Packard's Paper "On the Development of Limulus Polyphe- 

 mus," 1872. 



