777 



Proto. 



T al size 

 and discusses 

 the nature of 

 the animal, 

 which must 

 have had (1) 



in one species seven, in the other eight pairs of legs; or (2) 

 pairs of forked limbs like some living insects and crustaceans, 

 some two pronged, others three pronged, i e. a short broad 

 creature like our hexapods ; or (3) three pairs of forked legs, 

 and superadded smaller limbs, as in some living crustaceans, 

 by which odd pits were made ; or (4) a seven or eight pointed 

 fin or flipper of the proper shape to make the whole impres- 

 sion, first on one side and then on the other. But no creature 

 now exists to suggest such a mode of walking ; to sajr nothing 

 of the variations in the successive groups of prints. It is most 

 probable that the creature was a sort of crab, with limbs ar- 

 ranged as suggested by either (2) or (3) above. The great 

 King Crab {Limulus) comes nearest to realizing this idea, with 

 its small front pair, then four pair of forked legs, then a hind 

 pair with plate like appendages, and a long slender hard tail to 

 make the furrow. But the Lower Silurian ( Cambrian) animal 

 evidently moved forward, and not crab-like sideways. 



Protobalanus hamiltonensis, Whitfield. Bulletin of the 

 - ... jr ^ , j^ ..^, -^ ^, ^1 . . Am.Mus.N.Hist. 



Vlll-^ , ^ ^.M.^6^1. -;. ' P'^^^- N. Y. Vol. 2, No.. 



i-^ 2, 1889, page 67, 

 plate 13, fig. 22, 

 greatly enlarged 

 to scale, (same 

 as fig. 23, in Pal. 

 N. Y. Vol. 7, 

 page 209, plate 

 3 6; see foot 

 note.) The car- 

 inal plate of this 

 barnacle is sub- 

 M»Nj circular in out- 

 c^ v^/.2.##. YixiQ or semi-cir- 



