28 THE HABITAT OF THE EURYPTERIDA 



Pterygotus bilobus Salt., together with three varieties of this species, 

 P. raniceps (Woodw.), Slimonia acuminata (Salt.) and Stylonurus 

 logani (Woodw.) . The Pterygotus beds are followed by the "Trochus," 

 more properly, Platyschisma beds which correspond to the beds of 

 the same name in England, and which contain fragments of Slimonia 

 acuminata as do the next overlying beds which mark the transition 

 into the sandy Lanarkian series. 



The Lanarkian. About 1400 to 1500 feet above the base of this 

 series occurs a fish-band in the carbonaceous shales of which Euryp- 

 terus dolichoschelus (Laurie) has been found associated with Ceratio- 

 caris, five species of fishes, and Pachytheca and Parka. At another 

 locality seven species of fishes, Ceratiocaris, Dictyocaris, Pachytheca, 

 a Myriopod and Eurypterus dolichoschelus (Laurie) and Stylonurus 

 omatus (Laurie) have been found. 



Devonic. The Devonic formations of Great Britain have a better 

 representation of eurypterids than have those of North America. 

 The Old Red Sandstone of Forfarshire has yielded Pterygotus anglicus 

 in abundance and in a good state of preservation and one nearly entire 

 specimen of P. minor. From the same region come three species of 

 Stylonurus, S. scoticus, S. powriei, S. ensiformis, and finally the little 

 known Eurypterus brewsteri. In the Old Red Sandstones of England 

 occur Eurypterus pygmaeus and Stylonurus symondsii. Fragments 

 of Pterygotus problematicus have been reported from the Lower 

 Old Red of the Ludlow district. A few fragments of Eurypterus 

 hibernicus Baily have been found in the Upper Old Red of Kiltorcan, 

 Kilkenny County, Ireland. There are thus ten species of eurypterids 

 from the Devonic of Great Britain, all occurring in the Old Red 

 Sandstone facies of deposits associated with fishes, land plants, 

 fluviatile molluscs, myriopods and Crustacea, such as the fresh or 

 brackish-water phyllopod, Estheria, the ostracod Beyrichia and cer- 

 tain phyllocarids. With the exception of Pterygotus anglicus none of 

 the eurypterids is either abundant or well preserved, most of the 

 species being represented by a single portion of the exoskeleton or 

 by a number of fragments. Moreover, these fragments are scattered 

 in occurrence geologically and geographically. Six species are found 

 in Forfarshire, Scotland, in the Lower Devonic (Caledonian); three 

 species are sparingly represented in Brecknockshire and Herefordshire, 

 England, at the same horizon; while a few fragments of a single species 

 occur in the Upper Old Red of Ireland. 



Mississippic or Calciferotjs. The Calciferous fresh-water 



