Page:VCH Worcestershire 1.djvu/58

 A HISTORY OF WORCESTERSHIRE Here, too, are met with several small representatives of those remarkable Palaeozoic crustaceans known as trilobites, which take their name from the circumstance that the body, or middle portion of the carapace, is more or less distinctly divided into three longitudinal lobes. Externally trilobites present a distant resemblance to woodlice, but they were marine creatures related to the existing king-crabs of the Moluccas. They are very important to the palaeontologist, as their occurrence always indicates that he has to do with Palaeozoic rocks. The trilobites from the Malvern shales belong to the genera Olenus, Conocoryphe, Sphcer- ophthalmus, and Agnostus. In some of the shales the small Olenus humilis occurs in such profusion as to have suggested the name of ' Olenus shales ' for these particular beds. The green shales overlying the black shales in the neighbourhood of Hayes Copse contain a curious net-like fossil named Dictyonema socialis. This presents a considerable superficial resemblance to the modern lace-corals, but since its skeleton is not calcareous, and bears cups for the reception of polyps, it is considered to belong to the same group as the recent sertularians, or hydroid polyps. The invertebrate Silurian fossils of Worcestershire, although much more numerous in species than those of the Cambrian (and in certain localities exceedingly abundant in individuals), require somewhat less detailed notice than those of the last-named period for the reason that they are for the most part identical with those of the neighbouring counties. A large series of these fossils were collected by the late Dr. Grindrod, of Malvern, which are now in the Museum at Oxford, and there is also a fine collection in the Museum of the Malvern Field Club. Like those of other counties, the Silurian rocks of Worcestershire are characterized by the abundance of brachiopods, or lamp-shells, and cephalopods, or chambered molluscs ; gastropods, or ordinary univalve molluscs, and bivalves^ being much less abundant. In the May Hill Sand- stone (Upper Llandovery), which takes its title from the hill of that name in Gloucestershire, two very characteristic fossils are Fentremites oblongus and P. lens^ both easily recognizable by having vertical partitions within the valves ; they often occur in the form of casts. Other brachiopods from this formation are Atrypa reticularis, Orthis protensa, 0. calU- gramma, Strophomena compressa, S. antiquata, and Stricklandinia. Of these Atrypa and Stricklandinia are the most common. The two species of Pentamerus and Orthis calligramma occur in the May Hill Sandstone of the Lickey Hills, near Bromsgrove. Gastropods are represented by the nautilus-like Bellerophon and the spiral Murchisonia ; while the cephalopods include the long, straight Orthoceras barrandei and the less common Tretoceras bisiphonatum. Among tube-dwelling worms we have "Tentaculites ornatus and Cornulites serpularia. Trilobites, too, are abundant, but none are peculiar to this particular formation, such forms as Calymene blumenbachi and Phacops stokesi having a large vertical back, instead of right and left. 2S
 * Strictly speaking, lamp-shells are also bivalves, but in these the two valves are front and