Page:The Eurypterida of New York Volume 1.pdf/109

 Connected with this difference in rock is that in the aspect of the fauna. While the Eurypterus faunas of Buffalo and Pittsford consist almost entirely of mature and adolescent individuals, the younger growth stages prevail in the Shawangunk grit shales and large individuals are represented only by fragments which indicate that they may have been destroyed by the more turbulent water conditions farther out. On the other hand, the general absence of the earlier growth stages at Buffalo and Pittsford, together with the presence of the finer grained rock, intimate that there we have the habitat of the mature eurypterids which probably, was the somewhat deeper littoral, as in the case of Limulus, while the shale intercalations of the Shawangunk grit are the deposits of the shore pools in which the larvae were hatched and where the earliest stages of the ontogeny were passed, again as in the living Limulus.

An interesting analogy between this breeding place of the eurypterids in Orange county and that of Limulus rests in the fact that the young of Limulus are hatched on sandy tide flats and tide zones and the Shawangunk grit is a coarse sand deposit of this kind. It seems, therefore, a proper conclusion that the Shawangunk grit represents a tidal zone deposit of an encroaching sea or of a delta.

Omitting for the present the peculiar case of the Eurypterus horizons in the Frankfort shale and the Shawangunk grit and returning to the more typical Eurypterus facies represented by the waterlimes and shales of the Salina formation of western New York, we encounter the venerable and still current view that these beds were formed under conditions of much abnormal salinity. This view is based on the presence of the salt and gypsum