98 DE. T. DAVIDSON ON RECENT BEACHIOPODA. 



fixed close to the sloping portion of the upper edge of the septum, but later unite before 

 becoming reflected. Length 5 lines, width 4, depth 2J lines. 



Hah. This beautiful little species was dredged in large numbers by Mr. John Brazier 

 at South Eeef, Port Jackson, Heads and Pigs Eock, New South Wales. It was found alive 

 in the first-named locality, and presented a salmon-red colour. Dead perfectly white 

 specimens are to be obtained in large numbers. The ' Challenger ' Expedition obtained 

 it also at Port Jackson in from 2 to 4 fathoms. It is said to have been found also in 

 Bass's Straits, South Australia {=T. fibula, Eeeve). (See PI. XVII. fig. 33.) 



Ohs. When I described this species in 1852, only two dead specimens were known in this 

 country, and their habitat was uncertain. It is a very remarkable and excellent species, 

 but its exact generic position has been the theme of some difi'erence of opinion. Mr. L. 

 Beeve says, in his Revision of the Terebratulidse, Ann. & Mag. Nat. Hist. p. 11, 1861, that 

 " it is in my opinion neither a Terehratella nor a Magas. It begins to show internally 

 the caDous thickening both of the valves and of the apophysis of Bouclmrdia tulipa, and 

 is, above all, distinguished by the acuminated beak and terminal foramen peculiar to that 

 and to the following species " \_T. fihiduX I quite agree with him in this respect. There 

 exist also differences between it and McKjasella ; still, for all that, it is to the last-named 

 genus that the shell bears the strongest affinities, and I am disposed to coincide with 

 Mr. Dall in placing it in that genus. Magasella Cumingi varies a little, according to age, 

 in the manner in which its loop is attached to the sides of the mesial septum ; thus in 

 some specimens the anterior edge of the principal lamellae are fixed to the septum quite 

 independently of the upperanchor-shaped lamellae, which in those examples have a separate 

 attachment to the septum (PL XVII. fig. 30) ; again in other specimens the anterior edges 

 of the principal lamelkie cm've close along the sides of the septum, and become united to 

 the lower edges of the anchor-shaped pair previous to becoming reflected (PI. XVII. 

 fig. 31). 



In 1861, Mr. Lovell Beeve described and figured, in the paper already referred to, a 

 shell a little larger, but so similar in shape and character to Magasella Cummgi, by the 

 name of Terebratula (JSouchardia) fibula, that I am very much disposed to regard it 

 as nothing more than an unusually large example of M. Cumingi. Mr. Beeve states, 

 I. c. p. 180, that " This remarkable shell is curiously intermediate in its characters between 

 T. {Bouchardia) Cumingii and tidipa. The beak is more acuminated than in the former ; 

 and the area of the deltidium, which in B. Cnmingii and tulipa is excavately grooved, is 

 in B. fibula flat. In respect of the callous development of the interior, it is about inter- 

 mediate between the other two." 



I may, however, observe that we are acquainted with only one specimen of the so- 

 termed T. fibula, purchased by the British Museum from Mr. Calvert, a dealer in objects 

 of natural history. It measm-es 7 lines in length by 6 in breadth, and is consequently 

 larger than M. Cumingi, which does not seem to exceed 5^ to 6 lines in length where 

 it is usually found. The area in M. Cumingi is, it is true, usually excavated or concave, 

 but in some examples it is almost flat, and upon that slight apparent difference it 

 would not be right, I think, to record it as a separate species. The difference of habitat 

 may perhaps have been more favovu'able to the development of the single example of 



