Page:The Eurypterida of New York Volume 1.pdf/398

 directed backward can be distinctly seen on the carapace. A faint transverse depression separates the posterior fourth from the rest of the carapace.

Eyes. Whitfield and later Scudder [1886, p. 28] described the lateral eyes as situated on ridges near the antelateral borders, while Fritsch states that he saw three frontal eyes on the left frontal border of the eye lobe and therefore assumes that there may have been six altogether. He was the first to discern the contours of the large median eyes near the posterior margin. A small plain tubercle arising from a shallow depression is situated behind these eyes.

The specimen itself exhibits two distinct ocelli standing out like minute pearls in front of the eye lobe. There are much more minute tubercles on the left side of the ocelli which are of a distinctly different character. There is further seen on the left antelateral lobe of the carapace a small longitudinal series of four tubercles that, from their position and character, may well represent another group of lateral eyes.

Mesosoma. The mesosomatic segments forming the preabdomen have been the principal object of doubt. The upper side of the abdomen is cracked lengthwise; the left side is considered as the dorsal side, the right one as the ventral side by Whitfield and apparently also by Scudder. As a result of this conception of the fossil, it is inferred that the ventral side possessed, in distinction from all other scorpions, six subequal sternites; and as a further corollary, that since these supposed sternites exhibit no stigmata, the species was probably aquatic. Thorell, Pocock and Fritsch have criticized these inferences, and Thorell and Fritsch agree that only the dorsal plates are seen, the supposed ventral plates on the right-hand side being only the impressions of the dorsal plates that are broken away. Thorell bases his view mainly on the fact that the articulations of all the "ventral plates" are direct continuations of the articulations between the dorsal plates, which is not the case in the scorpions. The inspection of the specimen leaves no doubt that the ventral side of the preabdomen is not visible.

Fritsch has inferred from his study of the photograph that one sees indications of the organs of respiration on the right side in the 4th-6th