Family.
I. Lingulidæ, containing Lingula and other fossil genera.
II. Discinidæ, containing Siphonolreta and Discina.
III. Craniadæ, containing Crania.
IV. Productidæ, containing Chonetes and Productus, fossil.
V. Orthidæ, containing Calceola, Davidsonia, Strophomena, and Orthis.
VI. Rhynconellidæ, containing Atrypa, Pentamerus, and Rhynconella.
VII. Spiriferidæ, containing Uncites, Retzia, Athyris, and Spirifera.
VIII. Terebratulidæ, containing Thecidium, Agriope, Terebratella, and Terebratula.
[12] Woodward's Manual, p. 135.
[13] Is it necessary to say that even this account—apparently so well authenticated, not to speak of the representation drawn on the spot—should be taken "cum grano salis?"—Ed.
[14] The exceptions to these are the Doras, or flat-headed Hassar of India, which marches overland in large droves; the Swampines of Carolina (Hydrargyra); and the Perca Scandens, which in Tranquebar not merely walks over level ground, but climbs trees.
[15] Some fish, as the Chondropterygii, have no swimming bladder.—Ed.
[16] Dr. Fripp's theory of the properties of the fish's eye is very plausible.
1st. That the fish's eye in its normal state is arranged for the vision of near objects, and that the great refractive power of a prolate spheroid lens, such as exists in the fish, is adequate to the production of a picture at short focal distances, even with rays of light passing through so dense a medium as water.
2nd. That there is no accommodation of the fish's eye for extended limits of vision.
3rd. That the passive state of the fish's eye, being that in which it is enabled to see objects near and at moderate distance, no active or physiological change for accommodation of sight for distant objects takes place or seems necessary.