Moreover, a lower character is a very long coccygeal or caudal fin, which denotes that the anus lies far forwards, and therefore that the tail has a great preponderance over the trunk. In the Abdominales and the Sharks the tail is short; in the Rays thin and terminated abruptly, as in Reptiles and Thricozoa. Thus the higher the animals ascend the more does the tail diminish in length.
Regard being had to all these relations, the Irregular Fishes must be viewed as those which correspond to the lower classes of animals, and the Cartilaginous Fishes will indeed make the commencement; to these are annexed the Irregular Osseous Fishes, and nearest to them indeed those with arrested ventral fins, whether wanting or placed on the throat; then come the Regular Fishes, and of these first of all the Thoracici, and next the Abdominales. In this manner we obtain four divisions.
A. Body irregular.
I. Pisces Cartilaginei.
II. Stummelflosser—Apodales and Jugulares.
B. Body regular.
III. Thoracici—Tunnies, Breams, and Perch.
IV. Abdominales—Carps, Pikes, Salmons and Herrings, Sharks.
Now, these divisions, having been discovered by a simple analysis or testing of facts, are to be arranged according to philosophical principles, and further subdivided, whereby the ground and legality of their existence will be recognized.
A. IRREGULAR FISHES.
3535. Body deviating from the elliptical form, devoid of scales, or covered with spines, scutes, and plates; head and tail disproportionate; fins mostly arrested.
They correspond to the unarticulate Proto-and Conchozoa; their irregular-shaped mucous or mailed body agreeing perfectly with these animals.
Order 1. Intestinal, Protozooid Fishes.
3536. Mouth round and without maxillæ, or disproportionately narrow and wide.
There can be no doubt that the Lampreys are the lowest Fishes, since they remind us in every respect of the Worms by their naked, mucous, and lineiform body, with indistinct head, almost devoid of bones and true teeth, having a circular mouth, obliterated nostrils, puny eyes, and finally branchial cysts, which occupy a higher rank only from their opening into the pharynx. They pass therefore parallel to the Infusoria, or rather to the commencements of the second animal series, namely, the Etozoa Ancyliozoa.