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Show 1871.] MR. T. DAVIDSON ON JAPANESE BRACHIOPODA. 301 expeditions conducted by experienced naturalists, and extended to various latitudes ; but there remains still much to be done before the true specific claims of all the described species will have been determined ; even now Mr. W . H. Dall, of the Smithsonian Institution of Washington, has attempted a revision of the Terebratulidee, in an able and lengthened communication which will be found published m the sixth volume of the * American Journal of Conchotomy' (1 O T-~_\ • lo/0), to which I shall have to refer in the sequel. Fam. TEREBRATULIDEE, Cuvier. In his recent publications Mr. Dall has proposed to subdivide the family into the genera Terebratula, Terebratulina, Megerlia, Magas, Kraussina, Bouchardia, Platidia (=Morrisia), Megathy-ris ( - Argiope), 1 Thecidium, to which he adds as subgenera La-queus, Ismenia, Magasella, and Gist ella. Dr. Leopold v. Schrenk would also consider Rhynchonella to be a subgenus of Terebratula ; but in this view he will find but few supporters; and I regret likewise that Prof. Quenstedt should not have seen the propriety of frankly adopting Fischer de Waldheim's excellent genus Rhynchonella, one so clearly separated from Terebratula by the characters of its animal as well as by the structure of its shell. Ismenia Mr. Dall now relinquishes, having discovered that it is synonymous with Megerlia. Much difference of opinion has also been expressed as to the absolute necessity of substituting the term Megathyris for that of Argiope, a name previously made use of by Savigny for a genus of Egyptian Spiders. Mr. Jeffreys maintains that such a double application of the name in two different departments of zoology is not a reason for repudiating the second application of the same name, although such a practice ought to be avoided. The name Argiope has been in such general use for the shells to which it is referred, that I should regret to feel obliged to substitute that of Megathyris. If we examine the various species of which the genus Terebratella is composed, we shall perceive a certain amount of modification not only in the length and elevation of the median septum, but likewise of the point at which the lateral branches of the loop become attached to the septum, this connexion being much closer to the beak or to the front in some species than in others, the loop itself, as may be seen by comparing such species as T. dorsata or T. frontalis with T. spitzbergensis, being likewise much more developed in some forms than in others ; so that it becomes necessary to concede a certain variation in the internal details of the species of the same genus, and not to look upon each small deviation from the selected type as offering valid grounds for the creation of a separate subgenus. Mr. Dall proposes the adoption of a subgenus Magasella, of which m y Terebratella evansi would serve as a type ; but I feel more inclined to consider it a modification or subgenus of Terebratella than of Magas, from having noticed that in some species, such as M. flexuosa, the loop agrees exactly with that of Terebratella, while the |