OF CONCHOLOGY. 39 



SUPPLEMENT TO THE "REVISION OF THE TEREBRA.TTJ- 

 LIDiE/'WITH ADDITIONS, CORRECTIONS AND A REVI- 

 SION OF THE CRANIIDiE AND DISCINIDiE. 



BY W. H. DALL, SMITHSONIAN INSTITUTION. 



Since the publication of the paper above referred to, much new 

 material and many new facts have come to hand. To such an 

 extent has this been the case, that I have been impelled to offer 

 a supplement, which, besides containing additions and corrections, 

 should also furnish a ready list of the other species of recent 

 brachiopods not included in the first paper, so that the two taken 

 together might form for the student of these animals a sort of 

 index of reference. While doing this I am well aware that I 

 cannot hope to escape errors, and trust that such as may occur 

 may receive as speedy and thorough refutation as the progress 

 of science demands. Accuracy being the one thing needful in 

 all scientific work, no one should regret any advance toward it, 

 whether it militate for or against his individual views. 



I have to express my great obligations to various authors for 

 kindly and valuable criticism and assistance in my work, and to 

 none more than to Thos. Davidson, Esq., F. G. S., whose pale- 

 ontological studies among the members of this group, stand 

 almost unique among monographs, as do those of Barrande among 

 cephalopods and trilobites. To J. Gwyn Jeffreys, Esq. and Mr. 

 E. Billings I am under obligations ; I have also to express my 

 indebtedness to Prof. Agassiz, who, with the kind concurrence of 

 Count Pourtales and Dr. Win. Stimpson, has afforded me the 

 opportunity of examining and dissecting series of the brachio- 

 pods obtained in the well known deep sea dredgings of the U. S. 

 Coast Survey on the course of the Gulf Stream. The report 

 upon them will be published by the Museum of Comparative Zo- 

 ology. 



In the preliminary portion of my first paper on the Brachiopods, 

 I indulged in some brief remarks on the systematic position of 

 the group. These remarks were prompted, it is true, by some 

 recent publications of Prof. E. S. Morse, but were rather in- 



