The Geographical Distribution of Animals, Volume 2 / With a study of the relations of living and extinct faunas as elucidating the past changes of the Earth's surface

by Alfred Russel Wallace

Class.—BRACHIOPODA.

These are sedentary, bivalve, marine mollusca, having laterally symmetrical shells, but with unequal valves. Both in space and time they are the most widely distributed molluscs. They are found in all seas, and at all depths; and when any of the families or genera have a restricted range, it seems to be due to our imperfect knowledge, rather than to any real geographical limitations. In time they range back to the Cambrian formation, and seem to have had their maximum development in the Silurian period. It is not, therefore, necessary for our purpose, to do more than give the names of the families with the numbers of the genera and species, as before.

Family 1.—TEREBRATULIDÆ. (5 Genera, 67 Species living, 340 fossil.)

Family 2.—SPIRIFERIDÆ. (4 Genera, 0 Species living, 380 fossil.)

Family 3.—RHYNCHONELLIDÆ. (3 Genera, 4 Species living, 422 fossil.)

Family 4.—ORTHIDÆ. (4 Genera, 0 Species living, 328 fossil.)

Family 5.—PRODUCTIDÆ. (3 Genera, 0 Species living, 146 fossil.)

Family 6.—CRANIADÆ. (1 Genus, 5 Species living, 37 fossil.)

Family 7.—DISCINIDÆ. (2 Genera, 10 Species living, 90 fossil.)

Family 8.—LINGULIDÆ. (2 Genera, 16 Species living, 99 fossil.)