254 



THE HABITAT OF THE ETJRYPTERIDA 



tion 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. 



Lengths 



in millimeters 











CARA- 

 PACE 



PREAB- 

 DOMEN 



POSTAB- 

 DOMEN 



LAST POST 



ABDOMINAL 

 SEGMENT 



TELSON 



RATIO OF 

 CARAPACE 

 TO REST 

 OF BODY 



E. scorpionis 



E. newlini 



53 

 58 



67 



57 



I46 

 112 



40 

 34 



62 

 43 



O.I7:i 



0.23 : 1 





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 through- 

 out 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) ko- 

 komoensis, and E. ranilarva. Of the difference between these two 

 species Clarke and Ruedemann say: "It is possible that these differ- 

 ences are only those of sex, a point that at present cannot be deter- 

 mined 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. kokomoen- 

 sis 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. 



