BUFFALO SOCIETY OF NATURAL SCIENCES 243 



such pronounced ears on the epimera, although these are extended 

 posteriorly to a much more pronounced degree, than in 5. logani. 

 The only species which has epimera approaching in size and form 

 those of S. macro phthahnus is S. scoticus from the Old Red sandstone 

 (see p. 251 below), from which, however, it differs in certain important 

 features. It is closest to a second species found in the Old Red sand- 

 stone, S. powriei, which it resembles in the tapering form of the body 

 the long, narrow telson, the subquadrate outline of the head (this is 

 decidedly square in logani) and in the great length of the fourth 

 appendage. In details, on the other hand, these two species differ 

 considerably, so that S. logani must remain a rather separated species 

 until new discoveries reveal its relatives. It is of great interest to 

 have reported from the Ludlow fish bed in one of the tributaries of 

 Greenock Water (see p. 164 above) , Stylonurus ornatus associated with 

 the typical Lanarkian (Downtonian) fishes and with Eurypterus 

 dolichoschelus , a Ludlow and Lanarkian species, together with Cerati- 

 ocaris, Dictyocaris, plants, etc. (p. 164 above). S. ornatus, then, 

 evidently persisted from Wenlock into and through Ludlow time. 

 In this case one is again confronted with an anomalous geographic 

 and geologic distribution. The Pentland Hills are less than thirty 

 miles distant from the Lanarkian inliers, and the two areas are 

 approximately on the same line of strike. In two thin beds but a 

 few inches in thickness and extending only a few yards laterally 

 S. ornatus occurs in the Wenlock in Lanarkshire; but in the Pentland 

 Hills this species occurs in none of the many Ludlow eurypterid 

 horizons until the fish bed is reached and there a few specimens are 

 found. If the eurypterids lived in the Wenlock sea as they are 

 commonly supposed to have done, then the supporters of this view 

 must account for the limited vertical and horizontal distribution of' 

 the merostome remains, since it is absolutely inconceivable that mem- 

 bers of a marine neritic fauna should be confined to an area a few 

 square yards in extent. It is equally inconceivable that a marine fauna 

 should be perpetuated for so great a period of time as from the Wen- 

 lock through the Ludlow, the members of the later fauna in some 

 cases showing resemblance to members in the earlier, while in others 

 they are entirely distinct and apparently arise suddenly, there being, 

 besides, no indications of a persistent marine stock to furnish decend- 

 ants from the Wenlock fauna, nor yet any trace in the ma ine 

 Ludlow of the incursion from other regions of new genera and species 



