20 — GEOLOGICAL SURVEY 
Class—Reptilia —reptiles. 
“ Pisces —fishes. 
Sub-kingdom—Articulata—with external jointed Sub-kingdom—Mollusca—soft animals. 
skeletons. Class—Cephalopoda —feet around the head. 
Class—Crustacea —with anexternalhardcrust— “ —Gasteropoda —feet under the belly. 
crabs, §¢. “  __Pteropoda —winged feet. 
“ _Arachnida—spiders. “ __T,amellibranchiata—with lamellated gills. 
“ —Insecta —insects. “  __Brachiopoda —feet like arms. 
“ _-Anellata —worms. “  —Tunicata —covered with a man- 
“ __Ojrripedia —with curled feet. tle. 
Sub-kingdom—Radiata—radiated animals. 
roe ~ 
Nematoneura—with thread-like nerves. Acrita—aith obscure nerves. 
Class—Radiaria—rayed animals. 
— A. = 
a 
Echinoderma—with spinous skin. Acalepha—with stinging skins. 
Class—Polypi—polypes. 
Ciliobrachiata—with ciliated arms. Anthozoa—flower animals. Nudibrachiata—with naked arms. 
Class—Entozoa—internal animals. 
SS 
Coelelmintha—hollow worms. Sterelmintha—solid worms. 
Class—Infusoria—infusorial animals. 
rN 
Rotifera—wheel animalcules. Polygastria—with many digestive sacs. 
The preceding classification gives a pretty correct view of the present state of our knowledge in 
relation to the affinity existing between the classes and groups of the animal kingdom. The 
gradation between the classes of vertebrata is quite evident, beginning with the class mammalia, 
the most highly organized, and ending with the fishes, the lowest in the scale. The reptiles 
properly take precedence of the fishes; they have a higher organization. Many of them have 
feet, and all, to a certain extent, have the power of assuming a vertical position. Among the fishes 
the cartilaginous group stands lowest; and the “gar” of our coast, seems to connect the osseous 
fishes with the reptiles; for, besides other peculiarities, it has concavo-convex vertebre, and can 
move the head independently of the body.* 
But between the lowest animal, with a spinal column, and the highest without one, there is a 
vast gap in the scale. The sub-kingdoms, Articulata and Mollusca, cannot be arranged in a con- 
tinuous series, so as to exhibit the relative degrees of perfection of their organization ; for the 
highest class of Mollusca, the Cephalapoda, are far above the lowest class of Articulata, the 
Cirripedia. And, on the other hand, the highest of the Articulata are equally removed from the 
lowest of the Mollusca. The two sub-kingdoms must, therefore, be arranged in parallel series.— 
*Agassiz. 
