PALEOZOIC TIME — UPPER SILURIAN. 



665 



are referred to the Middle Silurian. It is a portion of the frond of a 

 Neuropteris. 



Animals. — The genera of Corals, Crinoids, Brachiopods, Trilobites, and 

 of other classes are to a large extent the same as in America. A Crinoid of 

 an unusual form is represented in Fig. 828, a Crotalocrinus ; Corals, in Figs. 

 826, 827 ; a common Fentamerus, in Fig. 829. 



Trilobites are common, as in the American rocks. Some of the species 

 are represented in Figs. 832-841. Figs. 832, 835, and 838 are of species 

 from the Wenlock ; Figs. 833, 834, 836, 837, 839, and 840 range below, and 

 all but 840 above, the Wenlock. 



Fig. 831, from Salter, is that of a large Limuloid, of the genus Pterygo- 

 tus, from the Wenlock beds. It shows well the chelate termination of the 

 antennae, but it is imperfect in wanting the four pairs of slender legs which 



832-841. 



841 



839 



838 



Tig. 832, Sphaerexochus mirus ; 833, a, Cheirurus bimucronatus ; 834, a, Encrinurus punctatus ; 835, E. varlolaris ; 

 836, a, Phacops Downingii ; 837, Acidaspis Brightii ; 838, A. Barrandii ; 839, Cyphaspis megalops ; 840, Proe- 

 tus latifrons ; 841, Hemiaspis limuloides. Figs. 832 to 840, after Murchison ; 841, after Woodward. 



are situated between it and the large posterior pair (see page 623). The 

 jaws in the figure, one of which is separately shown in Fig. 831 a, are the 

 basal portions of the posterior legs. 



Fig. 841 represents the Hemiaspis limuloides of Woodward, a form inter- 

 mediate between a modern Limulus and the Eurypterids; the genus has 

 species in both the Wenlock and Ludlow beds. 



A Ceratiocaris of the Ludlow group is shown in Fig. 842. Fig. 845, a 

 spine (referred to a genus of Sharks, Onchus), is supposed to be from a 

 Ceratiocaris. 



The first of Amphipod Crustaceans, Necrogammarus Saliveyi, is reported 

 from the Ludlow. 



A Scorpion has been found in the Upper Ludlow beds of Lesmahago in 

 Lanarkshire, Scotland, and in beds of nearly the same age in Gothland, 

 Sweden ; the latter is named the Palceophonus nuncius by Torell and Lind- 



