THE BRACHIOPODA OF TIIK SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 163 



rubicunda : is possibly its nearest ally, but, owing to the strongly developed septum, 

 its place in the genus TerebrateUa is precluded, and therefore it might possibly be 

 described as the magaselliform ancestor of T. rubicunda. 



In my opinion, judging from BUCKMAN'S figure, the original of which would appc:n 

 to be partly a cast, this form is more closely allied to one or other of the numerous 

 variations of the polymorphic T. dorsata. 



If comparisons be made with T. dorsata, var. submutica, F. and 0. (op. cit., 

 p. -279, pi. xi. figs. 1-6), a very striking resemblance is noticeable. In this variety 

 the radiating sculpture is almost absent, and the appearance of the shell is less 

 transverse than in the typical form. 



It might be argued, however, that the deltidial plates in these specimens are fully 

 developed, thus denoting an adult condition, but in examples of this form from 

 Burdwood Bank there are specimens which show the deltidial plates only partially 

 developed, and, as is usual in T. dorsata, the radiating ribs of the exterior are visible 

 also on the interior of the valves and would thus be impressed upon a fossil cast of 

 this species. 



To my mind it would be much more reasonable to refer the Cockburn Island fossil 

 to a magaselliform stage of TerebrateUa dorsata, and more especially to the var. 

 submutica, F. and O., than to go so far away as New Zealand for a comparison. 



According to FISCHER and OEHLERT (1892), T. dorsata is not cited among the 

 fossils of Patagonia by d'ORBiGNY. DARWIN, and SOWERBY, but on the contrary is given 

 by HUTTON (1873) and HECTOR (1886) for the New Zealand Tertiaries (Lower Miocene- 

 Ahuriri formation) from Cape Rodney, Auckland, N. Island, associated with the 

 recent Rhynchonella nigricans, Sow. 



This reference, if authentic, is of considerable importance as indicating significant 

 climatic changes during the deposition of these beds. 



One feels disposed, however, in the light of present knowledge, to question the 

 correct identification of the New Zealand species, and to consider the possibilities of 

 the form in question being referable to the well-known and variable T. cruenta or a 

 probable ancestor of that species. 



TerebrateUa sp. (PL II. fig. 10.) 



Hal). Station 346; lat. 54 25' S., long. 57 32' W. (Burdwood Bank), 56 

 fathoms. December I, 1903. Sea bottom, Bryozoa. Temperature 41 '8 F. 



Obs. Amongst the smaller specimens of Brachiopoda from this station are one or 

 two examples whose generic and specific positions are somewhat doubtful. 



The two largest and most perfect of these questionable forms measure : 



Lrngih. I'.nMiltli. Thickness. 



NM. 1 . . 13-25 10-5 6-75 nun. 



2 . . 1C 14 8-5 



^^H * A New Zealand recent species. 



(ROY. 80C. ED1N. TRANS., VOL. XLVIII., 385.) 



