ANALOGOUS TYPES. 107 
between those mentioned above, on account of 
the large shield of the Turtle. But there are 
Turtles with a soft covering, and there are some 
Toads with a hard shield over the head and neck 
at least, and both groups are alike distinguished 
by the shortness and breadth of the body and 
by the greater development of the limbs as com- 
pared with the lower Reptiles. But here again 
there is the same-essential difference in the mode 
of development of their young as distinguishes 
all the rest. The two series may thus be con- 
trasted : — 
Naked Reptiles. Scaly Reptiles. 
Toads and Frogs, Turtles, 
Salamanders, Lizards, 
Ceecilians. Serpents. 
Such corresponding groups or parallel types, 
united only by external resemblance, and dis- 
tinguished from each other by essential elements 
of structure, exist among all animals, though 
they are less striking among Birds on account 
of the uniformity of that class. Yet even there 
we may trace such analogies, —as between the 
Palmate or Aquatic Birds, for instance, and the 
Birds of Prey, or between the Frigate Bird and 
the Kites. Among Fishes such analogies are 
very common, often suggesting a comparison 
even with land animals, though on account of 
the scales and spines of the former the likeness 
