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 deter- 

 mined ; even now Mr. W. H. Dall, of the Smithsonian Institution of 

 Washington, has attempted a revision of the Terebrafulidce, in an 

 able and lengthened communication which will be found published 

 in the sixth volume of the 'American Journal of Conchology ' 

 (1870), to which I shall have to refer in the sequel. 



Fam. Terebratulid.e, Cuvier. 



In his recent publications Mr. Dall has proposed to subdivide 

 the family into the genera Terebratula, Terebratulina, Meyerlia, 

 Magas, Kraussina, Bouchardia, Platidia (=Morrisia), Megathy- 

 ris ( = Argiope), ? Thecidium, to which he adds as subgenera La- 

 queus, Ismenia, Magasella, and Cistella. Dr. Leopold v. Schrenk 

 would also consider Rhynchonella to be a subgenus of Terebra- 

 tula ; 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 Rhyn- 

 chonella, one so clearly separated from Terebratula by the cha- 

 racters 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 

 my Terebratella evansi would serve as a type ; but I feel more in- 

 clined 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 



