Page:The Habitat of the Eurypterida.djvu/262

254 of preservation found in the Bertie material. The characters are clearly enough shown to make it a certainty that this form has no relatives in the American faunas, so far known. Five specimens of Eusarcus newlini are known. This species, though attaining the gigantic size of E. scorpionis of the Bertie, shows marked differences in the proportions of the body. There is a general shortening up and broadening throughout. A set of figures taken from Clarke and Ruedemann's discussion will bring out this fact; some of the figures are only approximate.

It will be noted from these figures that although E. newlini, in the specimen measured, had a carapace 5 mm. longer than that of E. scorpionis the remainder of the figures for the other portions of the body are considerably less, showing that the proportions throughout are different. The ratio of the length of the carapace to the length of the rest of the body in the two species shows that in E. scorpionis it is as 0.17 : 1, while in E. newlini it is as 0.23 : 1. The cephalothoracic appendages are much stouter in E. newlini, with longer and stouter spines. Since the Bertie and Kokomo species of Eusarcus are the only ones in this country which are well enough preserved to allow of careful description, they are the only ones which can be compared and it has been shown that they do not show close relationship. The Kokomo fauna has yielded further two species of Eurypterus which are very similar, namely, E. (Onychopterus) kokomoënsis, and E. ranilarva. Of the difference between these two species Clarke and Ruedemann say: "It is possible that these differences are only those of sex, a point that at present cannot be determined since the opercular appendages of E. ranilarva are not distinctly shown" (39, 211). The proportions between the length and width of the cephalon in the Kokomo and Bertie forms are quite different. In E. ranilarva the ratio is as 7.1 : 10; in one specimen of E. kokomoënsis it is as 8 : 10, in another as 8.4 : 10, but in E. dekayi the ratio is only as 6 : 10 in one specimen and is even as low as 5.3 : 10 in another.