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 rachiopods 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 under- 
go a great expansion and development. This last is especially 
the case with the two families of the Sfzrzfertd@ and the Pro- 
ductide. The Sfirifers, 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 
S 
p 
ry, 
Rue 
<i AAS 
Fig. . — Spirifera " 
ae ce Fig. 96.—Spirifera mucronata. Devonian, America. 
nada. (After Billings.) (After Billings.) 
to such an extent as to have earned for them the popular name 
of ‘“fossil-butterflies.” The closely-allied Sfivifera disjuncta 
occurs. in Britain, France, Spain, Belgium, Germany, Russia, 
and China. The family of the Productide commenced to exist 
in the Upper Silurian, in the genus Chonefes ; 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 Preducte being represented by many forms of 
the allied group Productella. Amongst other well-known De- 
vonian Brachiopods may be mentioned the two long-lived and 
persistent types Atrypfa reticularis (fig. 97) and Strophomena 
rhomboidalis (fig. 98). The former of these commences in the 
Upper Silurian, but is more abundantly developed in the De- 
yonian, 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 Spzr7/er (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 wzder- 
stood. 
