ANGIOSTOMATA. Bl. The third family of Siphonobranchiata, Bl. described as differing little from the family of Entomostomata, but having long, narrow, straight apertures, and the columellar lips straight or nearly so. Were it not for the admission of the genus Strombus into this family, it would correspond with COLUMELLARIA and CONVOLUTÆ of Lamarck. ANNELIDES. The ninth class of invertebrated animals, divided into three orders, namely, A. Apodes, A. Antennés, and A. Sedentaires. The last only contains families of testaceous Mollusca. The animals are vermicular, some naked, others inhabiting shelly tubes. See SEDENTARY ANNELIDES. ANNULAR OPERCULUM is one which has the nucleus central, or nearly so, the other layers surrounding it in flattened rings. The term concentric is also applied. See Introduction. ANNULATED. (Annus, a ring.) Composed of, or surrounded by rings, as in the case of Tubicinella, fig. 14. ANODON. Brug. _Fam._ Submytilacea, Bl. Nayades, Lam. A genus composed of such species of NAYADES as are destitute of teeth on the hinge. Europe, North America, &c. An example is given in A. Cataractus, fig. 152. ANOMALINA. D'Orb. A genus of microscopic Foraminifera. ANOMIA. _Fam._ Ostracea, Lam. and Bl.--_Descr._ Irregular, inequivalve, sub-equilateral, foliaceous, pearly within; adhering to marine substances by means of a bony appendage, which passes through a large circular opening in the lower valve; muscular impression divided into three irregular portions; hinge destitute of teeth with a short cartilage.--_Obs._ The Linnæan genus included not only the shells to which the description above given would apply, but also many other genera, such as Crania, Orbicula, Terebratula, &c. which belong to the Brachiopoda, and are perfectly distinct. The Anomiæ are found in Europe, N. America, Moluccas, Philippine Islands, &c. Fig. 186, in the plates, is a somewhat reduced representation of a full grown specimen of A. Ephippium. Fig. 187, the hinge of the under valve, with the bony process. Fig. 188, the hinge showing the opening through which it passes. ANOSTOMA. See ANASTOMA. ANSATES. Klein. A genus formed of those species of Patella which have a produced, recurved beak. Helcion, Montf. _Ex._ Patella pellucida, fig. 230. ANSULUS or ANSYLUS. Mr. Gray conjectures that the name of the genus Ancylus, should be so written. ANTENOR. Montf. A genus of microscopic Foraminifera.