2 5 2 



THE HABITAT OF THE EURYPTEKIDA 



is a possibility that the marginal fold has been destroyed in the pos- 

 terior portions, but Woodward thinks that the specimen is entire, and 

 that the fold did not pass all the way around the carapace. S. 

 ensiformis is described from a single broken tail spine which, it seems 

 to the author, is hardly sufficient for the founding of a new species, 

 and certainly is of no use in determining the affinities of the fauna. 

 S. powriei, represented by a single individual, has a carapace very 

 similar in form and identical in proportions to S. scoticus, from which 

 species it differs most noticeably in having the last pair of append- 

 ages long and tapering, not short and broad. Woodward has sug- 

 gested that it probably had epimeral prolongations which have not 

 been preserved, because only the internal mold in sandstone has been 

 found, and the epimera would be likely to remain with the actual 

 integuments; for the same reason none of the surface markings are 

 visible. The tail is extremely long and narrow, quite similar to the 

 telson of S. logani from the Ludlow, which form it also resembles in 

 the character of the last pair of appendages. Both species belong to 

 the provisional group of Stylonurus s. st. recognized by Clarke and 

 Ruedemann. 



Completing the Old Red sandstone fauna are two species of Euryp- 

 terus: E. brewsteri and E. pygmaeus. The first consists of a carapace, 

 a portion of a thoracic segment slightly displaced, and an ovisac 

 containing more than twenty ova (Woodward, 312, 151). Wood- 

 ward says that "this species agrees most nearly in general form with 

 E. lacustris" from the Bertie, while Clarke and Ruedemann have 

 pointed out a close similarity to E. micro phthalmus from the same 

 horizon (39, 195). But since both authors make their comparison 

 on the form, proportions of length or width, and position of eyes, 

 and since the actual figures do not support either statement, I find 

 it impossible to agree with them. 



Eurypterus brewsteri 



E. lacustris 



E. microphthalmias, type 



E. microphthalmus. best preserved specimen. 



length or 



CARAPACE 



mm 



1.48 



44.00 



15-50 



17-5 



5-52 

 63.00 

 22 .00 

 27.40 



RATIO 



l:w 



0.27 

 o. 70 

 o. 70 

 0.64 



E. pygmaeus is a small form found near Kington, England, and 

 though represented by very young individuals, yet has characters 

 which point to its affinities with E. remipes (Fig. 28). 



