Page:The Eurypterida of New York Volume 1.pdf/274

 Horizon and localities. The four known specimens of this rare species, from Williamsville, Litchfield and Waterville, were obtained from the Bertie waterlime.

Remarks. Hall clearly set forth the peculiar characters of this species in the original description. He says "this species is distinguished by its robust, elongate body, the long straight-sided carapace, very anterior eyes, strong and thick jointed anterior feet, and extremely long swimming feet, with the great development of the terminal palette and the little dilation of the two preceding joints. The form of the postoral plate is very remarkable, though its posterior termination is unknown; the appendage is more prolonged and of a different form, and the adjacent articulation is very peculiar; and there are distinctive features in the maxillary plates."

The exceedingly long spines of the first three pairs of legs, the bractlike appendages of the fourth pair, and the great anteroposterior extension of the coxae of the last legs may be mentioned as further peculiar characters.

The powerful, long spined first legs indicate that  was an able walker and the bract-covered next pair of limbs, as well as the great elongation of the last pair, serve to demonstrate that it was likewise a powerful swimmer.

In consequence of the active use it made of its swimming legs, the species appears to have developed strong internal keels [pl. 43] within some of the segments corresponding to the entapophyses or internal keels and bars in recent arthropods, serving as attachment bases for powerful muscles.

The presence in the Frankfort shale fauna of at least one species with the characteristics of a Dolichopterus is demonstrated by a considerable number of carapaces and several metastomes. We refer these all for the present time to one species.

Description. Carapace subquadrate; length and width about equal; frontal margin very bluntly angular in the middle; lateral margins nearly