The eighth family, Veneridæ, includes Venus, Cytherea, Meroe, and Artemis; beautiful genera, and as such called by Linnæus and his followers after heroines of Greek mythology. Petricola, Venerupis, Tapes, Lucinopsis, and Trigona, also belong to the family. These acephalæ of size so small, like their congeners, inhabit every sea; they are found in every region of the globe, more than a hundred and fifty species being known. The shell is elliptic in form, the valves smooth, striated, spiny, and lamellous, like those of Cardium and Donax. Like these, they bury themselves in the sand. [Illustration: Fig. 142. Venus verrucosa (Linnæus).] [Illustration: Fig. 143. Cytherea geographica (Chemnitz).] Among the vast number of species, many of them are extremely rare, and much sought after by collectors in consequence of their great beauty. In the principal ports of France, _Venus verrucosa_ (Fig. 142), and another species known in the south of France under the name of Clovisse, are eaten there like oysters. Prepared with fine herbs, the Clovisse, we have M. Figuier's authority for saying, is not to be despised. "We may be believed also," he says, "if we add that nothing is more delicious than to eat the living Clovisse torn from the rock of the Phara of Lake Thau, when the Mediterranean sun of a day in winter is shining down upon us, the heart rejoicing in manhood's strength." In PL. XVIII. some of the principal species are represented, along with some of the more remarkable species of _Cytherea_. In Fig. 143 we have the elegantly pencilled shell of _Cytherea geographica_, together with the animal in its natural connection. The sub-section we shall now treat of is without the pallial line sinuated. The Cyprinidæ form the ninth family of our arrangement of the Conchifera, and contain, Cardia, Cypricardia, Isocardia, Crassatella, Astarte, Circe, and Cyprina, which amount together to some hundred species. The Cycladidæ are our tenth family, and include Cyrenoides, Cyrena, Pisidium, and Cyclas. The Lucinidæ is the eleventh family, containing Galeomma, Lepton, Montacuta, Kelia, Diplodonta, Corbis, and Lucina. In the small family of which we have made the Tridacna the representative, as well as in some preceding families, the mantle of the animal is more or less largely open, but never with such a prolongation as to form tubes. In the _Cardiums_, now under consideration, as well as _Donax_, _Tellina_, and _Venus_, the respiratory organs are somewhat modified, so as to adapt them to the habits of the animal. All these molluscs live buried in the mud or sand, and two great tubes issuing from the interior of their bodies bring the atmospheric air into communication with their respiratory organ--namely, the _branchial leaves_.