112 GUIDE TO THE FOSSIL INVEETEBEATE ANIMALS. 



Gallery Schmidtia from the Upper Cambrian of Eussia ; a mass of 

 VIII. Lower Llandovery sandstone with Pentamerus oUoiigus ; 

 Table-case ^^^^^^ q^.- Conchidium Aylesfordi from the Aymestry Lime- 

 stone, of its ally Sieberella galeata, and of Atrypa reticularis 

 from the Wenlock Limestone of Dudley ; blocks of Jurassic 

 Table-case Aidacothyris and various species of Bhynchonella ; 



Wall-case and slabs of Middle Lias, Great Oolite, and Cornbrash, with 

 11c. their characteristic brachiopods. 



The classification adopted in this Department is that used 

 in the English edition of Von Zittel's ' Palaeontology.' This 

 is based on the supposed evolution of the group, and may be 



Wall-cases followed in the Wall-cases, where the fossils from foreign 



localities are arranged in zoological order, beginning with 

 the top shelf and following its whole length from left to 



Fig. 58,— Types of Brachiopod Orders, a, Order Atremata, the Cambrian 

 Iphidea labradorica,' one of the simplest forms of brachiopod shell, b, 

 Order Neotremata, the Ordovician Orbiculoidea lamellosa, the pedun- 

 cular valve, showing the delthyrium, which has become surrounded by 

 the valve and partly filled in from underneath by a shelly deposit, 

 c, Order Protremata, the Ordovician Clitambonites Verneuili, seen 

 from the side of the brachial valve, above which is the lofty hinge-area 

 of the peduncle valve. The delthyrium is covered by a single pseudo- 

 deltidium, through which the peduncle passed by the foramen. 



right, and continuing on the middle and bottom shelves in 

 the same manner. By attending to this, the genera men- 

 tioned in the following account will readily be found. 



In those Brachiopoda that appear to be the simplest and 

 oldest, the shells are not as a rule joined by any hinge 

 (Diagram 7). These have therefore been called Inaeticulata 

 or ECAKDINES (e, without ; cardo, hinge) : they include Zin- 

 gula, Discina, Oholus, Crania, Trimerella, and their allies. 

 In more advanced forms, such as Orthis, Leptaena, Atrypa, 

 Terehratida, a hinge is developed at the hinder end of the 

 shell (Diagram 4), and these have been called Articulata or 

 Testicardines {testa, shell ; cardo, hinge). As classificatory 

 divisions, however, these are not altogether satisfactory, for 

 the Articulata are necessarily derived from the In articulata, 

 and intermediate forms are not rare. 



