Page:The Habitat of the Eurypterida.djvu/135

 unexpected as the fauna in the Shawangunk conglomerate. It is also not improbable that some of the tracks reported from the Hawick rocks were made by eurypterids, an interpretation in keeping with Patten's suggestion for the origin of Climatichnites (Patten, 206).

Following the retreatal phase of the Llandovery and the succeeding terrestrial phase of the Tarannon are the Wenlock beds. Though now exposed only in the southern belt below the tableland, in the small inliers in the Pentland Hills and Lanarkshire, and in the Girvan area, there is little doubt that the Wenlock at the time of its deposition extended entirely across this area. Such being the case, it represents the deposits of the advancing Wenlock sea. Continuous sections from the Tarannon into the Wenlock at various places in the belt south of the tableland show that the succession is conformable, thus proving that the line marking the end of the retreat of the sea must be northwest of this band and would lie, therefore, in the region of the tableland from which all Wenlock strata have, unfortunately, been removed. It is probable that the Tarannon-Wenlock shoreline was in the central or southern portion of the central belt. One of the finest exposures of the conformable contact of the Wenlock on the Tarannon is at Burrow Head, the outermost extremity of land between Luce and Wigtown bays just north of Solway Firth. The nature of the sediments along the belt south of the tableland indicates that oscillatory conditions prevailed, the seafloor being covered at times with fine muds, at others by coarse conglomerates. One would have expected that terrigenous deposits would have played a less important part there than in the Pentland Hills which are known to have been nearer the old shoreline. It is not unlikely that the land may have projected southward in a peninsula which lay between the present sites of Lanarkshire and Girvan, thus bringing the terrigenous sediments further south. In the southern belt there has been recorded a single occurrence of a eurypterid remain, so incomplete and so poorly preserved that it is specifically unidentifiable. Four miles south of Hawick at the junction of a small tributary with the Slitrig water Eurypterus sp. is reported associated with Ceratiocaris papilio and a number of graptolites. This type of occurrence, namely of a single eurypterid fragment associated with well-preserved abundant remains of marine organisms, has already been mentioned several times, and its significance pointed out. A general summary will be found below on page 194, in which the argument for the marine habitat of the eurypterids based upon such evidence is dealt with and, I trust, demolished for all time.