86 DR. T. DAVIDSON ON EECENT BRACHIOPODA. 



shell in the same condition, or a little older, G. B. Sowerby, in 1846, gave the name of 

 Terebratula inconspmict. In 1852 I expressed the opinion that the shell " seems to be 

 only a young and ill-gvown specimen of T. riihicmida;" and in this opinion S. P. 

 Woodward, E. Suess, and L. Reeve have concurred. Mr. Dall, however, maintains 

 it as a distinct species, and places it in his genus Ifagasella. When a little older, or at 

 about four or five lines in length, the septum becomes very much less elevated, and the 

 principal lamellge approach closely to the septum, where they become attached prior to 

 continuing their course and becoming reflected. In the adult or full-grown state the 

 septum is quite low, and at about half their length the principal lamellse, which are now 

 wide apart, give off a long, oblique lamella, which connects them to the anterior 

 extremity of the septum. A glance at the figures on Plate XV. will show these different 

 conditions better than any verbal description. 



Groups of specimens at different stages of growth are often found attached to a single 

 adult example. The shell is generally smooth throughout, but a tendency to plication is 

 not uncommon on the anterior portion of the shell. The peduncle is very short. 



Mr. Donovan states, in the second volume of his ' Naturalist's Repository,' that 

 Solander had given the MS. name of rubicunda to the shell we noAV kuow^ as Ki-aussina 

 rubra of Pallas, 1766 ; but as Solander did not publish his name, that of rubicunda, 

 Sowerby, must be retained for the shell under description. 



The intimate shell-structure of Terebratella rubicunda has been carefully investigated 

 by Dr. W. B. Carpenter. In plate iv. of his chapter on the structure of the shells 

 of Brachiopoda, contributed to vol. i. of my ' British Possil Brachiopoda,' he gives 

 three enlarged figures, one of these, which we reproduce (PI. XV. fig. 25), is a portion of a 

 vertical section of the loop-bearing valve, taken in the transverse direction through the 

 origin of the calcareous appendages, -nhich shows that the latter are not traversed by 

 canals. In this figure the ordinary trumpet-like form of the vertical passages is 

 shown, and the remarkable contractions which they exhibit in the inner and (probably) 

 later-formed layer ; in Plate XV. fig. 26 the occasional l)ifurcation of the vertical 

 passages is represented. 



43. Terebratella prontalis, Middendortf, sp. (Plate XV. figs. 1-8 a.) 



Terebratula frontuUs, Middenclorff, Beitriige zu einer Malacozool. Rossica, iii. 1849, Mem. Acad. St. 

 Pctersbourg, t. vi. p. 518 ; aud Reise in d. ausserst. Nordeu und Osten Sibiriens, 1851, Bd. ii. jj. .LMl, 

 t. xviii. figs. 9-li; E. Suess, Ueber die Wohnsitze der Brachiopoden, Sitzungsb. k. Akad. der Wissensch. 

 Wien, p. 204, 1859; Dall, Amer. Jourii. of Conch, vol. vi. p. 1.23, 1870; Proc. Acad. Nat. Sci. 

 Philadelphia, 1873, p. 184 ; Dall, Report on the Brachiopoda of Alaska and the adjacent shores of North- 

 west America, ibid. 1877, p. 15G; Duuker, Index Mollusc, maris Japonic!, p. 252, 1882. 



Shell somewhat subpentagonal, longer than wide, broadest about the middle, mar- 

 ginally curved, slightly indented in front. Dorsal valve posteriorly evenly convex, 

 anteriorly divided by a narrow^ longitudinal depression or groove, commencing at a very 

 short distance from the front margin. Ventral valve rather deeper than the dorsal one, 

 w^ith a very slight elevation close to tlie margin; beak rather large, truncated at right 

 angles by an unusually large incomplete foramen, posteriorly margined to a considerable 



