484 



FOSSILS OF LOWER LUDLOW. [Ch. XXVII 



Fig. 575. 



Fie. 5T6. 



Atrypa reticularis, Linn. (Terebratula affinis, Min. Con.) Aymestry. 

 a. Upper valve. 6. Lower valve. 



c. Anterior margin of the valves. 



The Aymestry Limestone contains so many shells, corals, and trilobites 

 agreeing specifically with those of the subjacent Wenlock limestone, that 

 it is scarcely distinguishable from it by its fossils alone. Nevertheless, 

 many of the organic remains are common to 

 the Aymestry limestone and the Upper Lud- 

 low, and several of these are not found in the 

 Wenlock.* 



3. Lower Ludlow shale. — This mass is a 

 dark gray argillaceous deposit, containing, 

 among other fossils, many large chambered 

 shells of genera scarcely known in newer 

 rocks, as the Phragmoceras of Broderip, and 

 the Lituites of Breyn (see figs. 576, 511). 

 The latter is partly straight and partly con- 

 voluted, nearly as in Spirula. 



Phragmoceras ventricnsvm, J. Sow. The OrthoceraS LudenSe (fig. 578), as 

 ( Orthoceras ventricosum, Stsin.) ,, ,, . ■. , , , . 



Aymestry ; i nat. size. well as the cephalopod last mentioned, la 



Fig. 57T. 



peculiar to this member of the series. 



Fig. 5T6. 



Lituites giganteus, J. Sow. 

 Near Ludlow ; also in the Aymestry 

 and Wenlock limestones ; i nat. size. 



Fragment of Orthoceras Ludense, J. Sow. 

 Lcintwardine, Shropshire. 



A species of Graptolite, G. Ludensis, Murch. (fig. 588, p. 437), a form 

 of zoophyte which has not yet been met with in strata above the Silurian, 

 occurs plentifully in the Lower Ludlow. 



* Murchison's Siluria, p. 133. 



