2l8 THE HABITAT OF THE EURYPTERIDA 



domina, and one with a portion of a leg, so early in the Ordovicic in 

 muds derived from Appalachia is most suggestive. In the succeed- 

 ing Schenectady beds in the same general region, in muds also washed 

 down from Appalachia, occur a number of specimens which, in the 

 shape of the carapace, position of the eyes, etc., suggest their generic 

 reference to Stylonurus and have been described by Clarke and Ruede- 

 mann as S.? limbatus. They have furthermore found a number of 

 body segments "which have the form and ornamentation of the Otis- 

 ville species Stylonurus myops" (39, 296). Although it is a little out 

 of chronological order to bring in the Utica species before taking up 

 the Schenectady fauna, this, nevertheless, is the logical place for its 

 discussion. Echinognathus clevelandi was described from a single 

 endognathite which has shown two diagnostic characteristics, namely, 

 an extreme spinosity, and a peculiar and distinctive type of surface 

 sculpture. Clarke and Ruedemann state that this species "was 

 either closely related to Stylonurus or had a convergent development 

 to that genus as far as the two characters mentioned are concerned" 

 (39, 322). It may quite properly be asked why it is that if the single 

 endognathite known, shows only two diagnostic characteristics, and 

 these two are recognized as definitive of Stylonurus, the species does 

 not belong to that genus, or at least is it not more than likely, if 

 more specimens are discovered, showing other parts of the body, 

 they will be found to represent Stylonurus? It seems to the author 

 that the geographical and geological position of E. clevelandi alone 

 would suggest the greater possibility of the form being a Stylonurus. 

 To be sure, this is somewhat speculative, but it is a suggestion for 

 future work and consideration; it is sufficient that the Utica species 

 is at least closely related to the genus Stylonurus which was found 

 at earlier periods and also in the Siluric and Devonic, always in de- 

 posits derived from Appalachia. This statement includes the Utica 

 beds just mentioned, for it is now recognized that, as Professor Gra- 

 bau first pointed out, the muds were carried down from Appalachia 

 and were merely the eastern near-shore facies which replaced that of 

 the Trenton limestone facies (Grabau, 84, 231-232). Passing on to 

 the next time in the history of North America when the genus Sty- 

 lonurus is known to occur, we find 5. (Ctenopterus) multispinosus in 

 the Pittsford and two well defined species of this genus, as well as 

 many fragments specifically indescribable though evidently distinct in 

 the Shawangunk, both of which formations have been interpreted on 

 stratigraphic grounds and on a comparison of the two faunas inter 



