.306 NEW YORK STATE MUSEUM 



traction in E. maria is not long retained. Plate I, figure 2 

 shows an entire specimen with a full supply of segments and with 

 relatively broader abdomen than in the mature form but its outline 

 gradually rounds to the more slender posterior segments. The 

 length of this specimen is 8 mm. In the incomplete individual 

 shown in figure 4 of the same plate all the essential features, of 

 maturity appear to have been assumed, even the eyes and ocelli 

 having their normal development. This fragment represents an 

 animal probably 10-11 mm in length. 



The variability of the eyes in size and position in these young 

 phases invites special attention. We have figured on plates 2 and 3 

 a considerable number of these head shields and it will be observed 

 on consulting these figures and their accompanying natural size out- 

 lines that while there is no direct relation between the size of the head 

 and the size and position of the eyes the instability of these features 

 loses itself on the approach to adult size. Accompanying these 

 changes there is an equally irregular variation in the outline of the 

 head which from being short and almost semilunar gradually 

 approximates the more elongate form of the ephebic type [pi. 2, 

 fig. 2]. 



We may therefore summarize the ontogenetic changes, derivable 

 from the evidence which this species presents as follows : ( 1 ) Very 

 early change from the scorpioid to the gently tapering abdomen; 

 (2) gradual but irregular increase in segmentation; (3) gradual 

 but irregular elongation of the head ; (4) highly irregular variation 

 in position of the eyes, but gradual travel from the margins inward 

 to their normal locus. 



Eurypterus my ops no v. 



Plate 6, figures 1-5, 6 (?) 



This species is in many respects a diminutive expression of 

 Eurypterus pittsfordensis Sarle, the head (all that is 

 now known of it) being subquadrate, almost as much squared in 

 front as behind, the eyes large, semicircular, subcentral and approxi- 

 mate and the ocellar mound developed in mature forms. The 

 material is insufficient to establish any marked variations in growth, 

 as the species is among the less common forms of the fauna. One 

 example shown in figure 6, which is doubtfully referred to the species 

 has the eyes large and almost marginal. There is a striking simi- 

 larity between this species and the last of the Eurypterid race, the 

 Eurypterus described by de Lima from the Permian of Bussaco, 

 Portugal. 



