Page:The Eurypterida of New York Volume 1.pdf/184

  as 6:9 (8.5–10); and in the different outline; the former having a squarish carapace with subparallel sides and straight frontal margin and subrectangular anterior angles, while in the latter species the sides are more convergent and the anterior angles more rounded. Specimens are, however, common which it is difficult to assign to either species, partly on account of their original intermediate form and partly because of secondary changes through lateral compression. The average representatives of  are considerably larger than those of   although a few carapaces of the latter species indicate that it did not fall much short of the other type in size attained. Nevertheless the great majority of the specimens of  obtained in the central New York region are very much smaller. No differences have been observed in the proportions of the abdomen and the appendages (including the metastoma), save perhaps the swimming legs, in which a tendency to greater broadening is observable in, and this has led to the variety.

A variety  of the present species has been distinguished by Hall, in regard to which it is stated that: "The form of the anterior feet and the swimming feet are essentially the same, while the joints of the body are proportionately longer and stronger, furnishing sufficient ground for a variety, but not satisfactory evidence of specific difference." In the explanation of his figures [plate 81C] a note is added saying that further examination with other species has shown that the form has the characters of a distinct species. The difference supposed to rest in the greater length and strength of the abdominal segments is due to the postmortem separation of the segments as far as the stretching of the connecting membranes permitted, while on the other hand, Hall's types of  are all somewhat contracted through sliding of the segments over each other. We have been unable to find other differences and therefore consider  as only a preservation state.