Page:The Habitat of the Eurypterida.djvu/31

 occurring also in the Temeside group. Eurypterus pygmæus Salt. and Stylonurus megalops Salt. are common as fragments in the higher olive shales of the Temeside group. Pterygotus banksii Salt. together with numerous indeterminable species of Eurypterus are found in the Ludlow Bone-Bed; this species is also common in the Platyschisma bed and the upper olive shales of the Temeside group; in the same shale P. ludensis Salt. is abundant. In all cases where species are reported to be common it is to be remembered that no entire specimens are found but only fragments and disjecta membra. The occurrences cited are from the Ludlow district in Shropshire; to the south-west in the Downton Castle sandstone at Kington in Herefordshire Pterygotus banksii has been found in large numbers associated with P. gigas, the spines of crustacea and fish and also Platyschisma helicites and Lingula cornea. Salter has further described Eurypterus abbreviatus from a single telson which he found at Kington. Brodie collected specimens of Pterygotus banksii, Eurypterus pygmaeus, E. acuminatus, and E. abbreviatus at Purton, Herefordshire. The greatest abundance of specimens is found in a sandy marl lying just below a yellow sandstone containing plants, seed-vessels of Lycopodiaceae and fragments of eurypterids. The horizon is about that of the Ludlow Bone-Bed (24, 236).

The Ludlow of Scotland is found only in a few inliers in Lanarkshire. Division 3 recognized by Peach and Horne (215) consists of flagstone and greywackes with Ceratiocaris beds and containing the Ludlow fish band. From these beds Slimonia acuminata Salter has been described associated with five species of Ceratiocaris and worm tracks. From the same shales Pterygotus bilobus Salter and the common Ludlow fish Thelodus scoticus are reported. In certain places occur Beyrichia kloedeni and Platyschisma helicites forms very frequently associated with Upper Siluric eurypterids. The fish band contains Slimonia acuminata, the myriopod Archidesmus loganensis Peach, four species of the phyllocarid crustacean Ceratiocaris and one of Physocaris, together with numerous fish fragments and two species of Thelodus. Of great interest has been the discovery by Peach in this fish band of one of the oldest scorpions from Great Britain, Palaeophonus caledonicus Hunter. This is approximately the same horizon at which Lindström found Palaeophonus nuncius in Gotland (see below, p. 34). The eurypterid horizon par excellence occurs in the next higher division above the fish band and contains Eurypterus lanceolatus (Salt.), Eusarcus obesus (Woodw.), E. scorpioides (Woodw.),