THE NATATORIAL FORM. 253 



potamus, or river horse, but for the extreme shortness of 

 its legs, would vie in bulk with the elephant : this 

 also is a natatorial type, and we find it possessed of all 

 the leading characters, under new modifications : a large 

 head, thick and blunt snout, short and imperfect feet, 

 and aquatic habits, leave the analogy indisputable. The 

 ostrich is the largest bird in existence : it is not nata- 

 torial, because it belongs to a different order ; but nature 

 has contrived that all the other indications of its type 

 should be preserved: the bill (corresponding to the 

 snout of quadrupeds) is broad, depressed, and obtuse, 

 and the wings (the chief organs of motion among birds, 

 as feet are among quadrupeds,) are so short as to be 

 almost useless. Crabs, among annulose animals, are 

 the largest and the most aquatic of all wingless insects 

 (Apterq L.), for in that division were they placed by 

 Linnaeus, and to that they truly belong : the head is 

 enormous, and in many is so confounded with the thorax 

 that the two parts appear but one. If we pursue the 

 analogy to the winged orders (Ptilota), we find the 

 gigantic Neuroptero J} at the head of which stand the 

 dragon-flies, living the greater part of their lives in 

 water, and the genus Mantis far surpassing all other 

 insects in bulk. We shall hereafter endeavour to point 

 out the probable station of those stupendous fossil rep- 

 tiles, the ichthyosaurus, plesiosaurus, &c., and which we 

 consider as constituting the natatorial type of the 

 Reptilia; preserving, even in their fossil remains, all the 

 properties of such types. Now, to prove that these 

 examples are not taken at random, but are actually sup- 

 ported by analysis, we shall place before the reader 

 a table of the aberrant types of some of the groups we 

 have here intimated : 



Aberrant Group of the 



Series of Series of Verte- Series of the Series of the Series of 

 Quadrupeds. brata. Pachydermata. Rasores. the Ptilota. 



Ungulata. Reptiles. Megatherium. Guan. Hymenoptera. 

 Glires. Amphibia. Hyrax. Pigeon. Coleoptera. 

 Cetacea. Fishes. Hippopotamus. Ostrich. Neuroptera* 



