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 _Orthis, Strophomena, Lingula, Athyris_, and _Rhynchonella_, we find some entirely new ones; whilst various types which only commenced their existence in the Upper Silurian, now undergo a great expansion and development. This last is especially the case with the two families of the _Spiriferidoe_ and the _Produclidoe_. The _Spirifers_, in particular, are especially characteristic 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 to such an extent as to have earned for them the popular name of "fossil-butterflies." The closely-allied _Spirifera disjunda_ occurs in Britain, France, Spain, Belgium, Germany, Russia, and China. The family of the _Productidoe_ commenced to exist in the Upper Silurian, in the genus _Chonetes_, and we shall hereafter find it culminating in the Carboniferous in many forms of the great genus _Producta_[17] 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 _Produdoe_ being represented by many forms of the allied group _Productella_. Amongst other well-known Devonian Brachiopods may be mentioned the two long-lived and persistent types _Atrypa reticularis_ (fig. 97) and _Strophomena rhomboidalis_ (fig. 98). The former of these commences in the Upper Silurian, but is more abundantly developed in the Devonian, having a geographical range that is nothing less than world-wide; whilst the latter commences in the Lower Silurian, and, with an almost equally cosmopolitan range, survives into the Carboniferous period. [Footnote 17: 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, grammatically incorrect, as the feminine noun _cochlea_ (shell) is in these cases _understood_.] [Illustration: Fig. 98.--_Strophomena rhomboidalis_. Lower Silurian, Upper Silurian, and Devonian of Europe and America.] [Illustration: Fig. 99.--Different views of _Platyceras dumosum_, of the natural size. Devonian, Canada. (Original.)]