PERMIAN AGE AND CLOSE OF THE PALEOZOIC. 181 



continental oscillations during the Palaeozoic. Do we 

 know anything of law in the case of life ? The question 

 raises so many and diverse considerations that it seems 

 vain to treat it in the end of a chapter ; still we must 

 try to outline it with at least a few touches. 



First, then, the life of the Palaeozoic was remarkable, 

 as compared with that of the present world, in pre- 

 senting a great prevalence of animals and plants of 

 synthetic types, as they are called by Agassiz — that is, 

 of creatures comprehending in one the properties of 

 several groups which were to exist as distinct in the 

 future. Such types are also sometimes called em- 

 bryonic, because the young of animals and plants often 

 show these comprehensive features. Such types were 

 the old corals, presenting points of alliance with two 

 distinct groups now widely separated; the old Trilo- 

 bites, half king-crabs and half Isopods ; the Amphibians 

 of the coal, part fish, part newt, and part crocodile ; the 

 Sigillariae, part club-mosses and part pines ; the Ortho- 

 ceratites, half nautili and half cuttle-fishes. I proposed, 

 in the illustration in a former article, to give a restora- 

 tion of one of the curious creatures last mentioned, the 

 Orthoceratites ; but on attempting this, with the idea 

 that, as usually supposed, they were straight Nautili, 

 it appeared that the narrow aperture, the small outer 

 chamber, the thin outer wall, often apparently only mem- 

 branous, and the large siphuncle, would scarcely admit 

 of this ; and I finished by representing it as something 

 like a modern squid; perhaps wrongly, but it was 

 evidently somewhere between them and the Nautili. 



