Of the fauna of the Dyas Credner remarks that it is much poorer than that of Carboniferous times, and with the exception of a few reptiles and fishes, limited to the marine formation of the series. of all the lower forms Brachiopoda are by far the most prevalent, and furnish the most characteristic and most widely distributed of Zechstein remains. Lamellibranchiata assume, however, an importance unknown to them in earlier periods, and in their general character tend more towards Mesozoic than Palæozoic forms; he even suggests that Schizodus may be considered the ‘precursor (Vorläufer) of the Trigonia’