DEVONIAN AND OLD RED PERIOD. 147 



"cells," which are generally borne in rows on the branches, 

 and of which each originally contained a minute animal. 



The Brachiopods still continue to be represented in great 

 force through all the Devonian deposits, though not occurring 

 in the true Old Red Sandstone. Besides such old types as 

 On 'his, Strophoinena, Lingula, Athyris, and Rhynchonella, we 

 find some entirely new ones ; whilst various types which only 

 commenced their existence in the Upper Silurian, now under- 

 go a great expansion and development. This last is especially 

 the case with the two families of the Spirifcrida and the Pro- 

 ductidce. The Spirifers, in particular, are especially character- 

 istic of the Devonian, both in the Old and New Worlds some 

 of the most typical forms, such as Spirifera mucronata (fig. 96), 

 having the shell " winged," or with the lateral angles prolonged 



- . 



scnlfiiilis. Devonian, Ca- Fig. &.Sf*rifera mucronatn. Devonian, America, 



nada. (After Billings.) (After Killings.) 



to such an extent as to have earned for them the popular name 

 of " fossil-butterflies." The closely-allied Spirifera disjuncta 

 occurs in Britain, France, Spain, Belgium, Germany, Russia, 

 and China. The family of the Productidcz commenced to exist 

 in the Upper Silurian, in the genus Chonetes ; and we shall 

 heieafter find it culminating in the Carboniferous in many 

 forms of the great genus Producta * itself. In the Devonian 

 period, there is an intermediate state of things, the genus 

 Chonetes being continued in new and varied types, and the 

 Carboniferous Products being represented by many forms of 

 the allied gronp Productella. Amongst other well-known De- 

 vonian Brachiopods may be mentioned the two long-lived and 

 persistent types Atrypa relicularis (fig. 97) and Strophomcna 

 rhomboidalis (fig. 98). The former of these commences in the 

 Upper Silurian, but is more abundantly developed in the De- 

 vonian, having a geographical range that is nothing less than 

 world-wide; whilst the latter commences in the Lower Silurian, 



* The name of this genus is often written Productus, just as Spirifera 

 is often given in the masculine gender as Spirifer (the name originally given 

 to it). The masculine termination to these names is, however, grammati- 

 cally incorrect, as the feminine noun cochlea (shell) is in these cases under- 

 stood. 



