Mr. T. Davidson on Recent Terebratulse. 33 



more than a subgeneric distinction ; but when we come to place 

 it in comparison with Terehratella or any of its modifications, 

 the difference is more apparent. It is not impossible, I admit 

 that these extremes may be found to be far more nearly, con- 

 nected than is at present supposed; and many observations 

 in connexion with the fossil species would lead to that inference. 

 In Waldheimia, where, like Terebratula, we have but a single 

 attachment, the loop is long and reflected, and there exists a 

 medial! septum ; so that all that would be required for a Wald- 

 heimia to be converted into a Terehratella, so far as the shape of 

 the loop is concerned, would be for the principal stems of the 

 loop to effect a second attachment to the abeady existing septum 

 by means of short shelly processes. 



I have made these observations and given these few examples 

 (taken from among many) in order to show how difficult it is 

 to rest long on a single character ; for we have seen what a ten- 

 dency the loop possesses to become modified at different ages 

 and in certain forms, and how it thus diminishes in value as a 

 constant character; but still, for all that, and until a better 

 mode of classification presents itself, I think there is an advan- 

 tage in subdividing the TerehratulidcB as we have done, with the 

 understanding that undue importance must not be attached to 

 the divisions. 



Several new species having likewise turned up during the last 

 few years, a revision of the subject had become not only a desi- 

 deratum but an absolute necessity ; and this has been most ably 

 accomplished by Prof. Suess and Mr. L. Reeve. It must be 

 remembered that Prof. Suess^s ' Wohnsitze ' has for its subject 

 the fossil as well as the recent species, from the conscientious 

 study of which he has deduced certain interesting philosophical 

 reflections : but the author does not pretend that his superstruc- 

 ture is faultless; on the contrary, he claims great indulgence 

 from having been obliged to borrow information from several 

 sources which he could not possibly verify ; and I do not con- 

 sider that the author has shown any disregard for details or 

 want of acumen in the preparation of his work*. Prof. Suess's 

 * Wohnsitze ' was not intended to take the place of a monograph 

 of the recent Brachiopoda, as the author neither gives illustra- 

 tions nor complete descriptions of the various species ; so that 

 Mr. Reeve's " Monograph of tiie Genus Terebratula," which 

 forms a part of his valuable and beautiful * Conchologia Iconica, 

 really fills up one of the desiderata to which we have already 



* We feel much pleasure in refevrinw the reader to a verj' interesting 

 analysis of Prof. Suess's memoir, from the pen of the distinguished French* 

 naturalist, M. Deshayes, which will be found in the Bulletin de la Soc. 

 Geol. de France, 2 ser. vol. xviii. p. 163, 1861. 



Aim. 4)- Mag. N. Hist. Ser. 3. Fo/. viii. 3 



