DE. T. DAVIDSON ON EECENT BEACHIOPODA. 79 



protecting wall to tlir^ 'viscera ; . . . The arms in Ter. chilensis, when detached from the 

 supjoorting processes and unfolded, exceed the length of the shell by two thirds of that 

 length ; and their length is to their breadth as eight to one. Their stem, from which 

 the cilia airse, as it has not to execute the movement of Lingula, so it is much more 

 slender. The cilia, therefore, are proportionally increased, in order to excite the neces- 

 sary currents in the Avater ; which, being directed between the folds of the arms 

 towards the mouth, as to a focus, carry thither tlie nutrient molecules, which are retained 

 by the natural sieve formed by the decussating cilia of the terminal processes in front of 

 the mouth ; and though this apparatus is apparently less perfect than in Limjula, it is 

 evidently adjusted in due relation to the support of so small a mass of body as exists 

 in Tercbratula." 



Prof. Owen then refers to the muscles and peduncle; but as these bear a general 

 resemblance to those already noted in Waklheimia and in other genera, we will not 

 repeat his description here. He also describes the alimentary canal, the oesophagus, 

 and liver: this last he states to be "a bulky gland of a green colour and minute 

 follicular texture ; it is disposed in two principal masses, which lie on each side of the 

 alimentary canal, and between the two lateral arches of the testaceous loop iu tho^p species 

 of Terehmtula which possess that appendage ... In two of the larger specimens of 

 Ter. Sowerbii, the ova were lodged external to the liver, and had also insinuated themselves 

 between the layers of the mantle-lobes, in close proximity to, and partly surrounding, 

 the branchial vessels. They are probably discharged in this way from the mantle, 

 having previously been exposed to the influence of the branchial currents. ... In 

 dissecting a Terehratula I have found it most convenient to cut transversely through the 

 perforate valve, so as to leave the orifice and the pedicle connected to the opposite valve, 

 by which means the disposition of the muscles is satisfactorily seen, and the delicate parts 

 within are less liable to be disturbed than by attempting to separate the entire valve." 

 I regret not being able to reproduce Prof. Owen's admirable illustration. 



The muscular system of Terehratula dorsata has also been described by Prof. W. King 

 in the Ann. & Mag. Nat. Hist. ser. 1, vol. xviii. p. 39, 1846. 



38. Terebratella transversa, Sowerby, sp. (PI. XVI. figs. G-9.) 



Terebrutula Iramversa, G. B. Sowerby, Descriptions of thirteen new Species of Brachiopoda, Proc. Zool. 

 Soc. 184G, p. 91 ; Tlies. Conch, vol. i. p. 3G1, ])1. 72. figs. 114, 115, 1846. 



Terehratula caurina, Gould, Proc. Boston Soc. Nat. Hist. iii. p. 347, 1850 ; Gould, U. S. Esplor. Exped. 

 xii. Shells, p. 468, pi. 44. fig. 582 ; Otia Conch.p.97, 1862; Carpenter, Supp. Rep. Brit. Assoc. 186.3, p. 636. 



Terebratella caurina, E. Suess, Ueber die Wohnsitze der Brachiopodcn, Sitzungsb. k. Akad. Wissensch. 

 Wien, Bd. xxsvii. p. 207, 1859. 



Terebrutula canrena, P. P. Carpenter, Rep. Brit. Assoc. 1856, p. 298. 



Terebratula (Terebratella) transversa, L. Reeve, Conch. Icon. INIonog. Ter. pi. v. fig. 22, I860 ; A Revision 

 of the History, Synonymy and Geograxihica! Distribution of the Recent TerebratuLe, Ann. & Mag. Nat. 

 Hist. 3rd ser. vol. vii. ]>. 176, 1861. 



Terebratella caurina, Dall, Amer. Journ. of Conch, vol. vi. p. 119, pi. vi. figs. 1, 2, 3, 1870. 



Terebratella occidentalis, Dall, Proc. Acad. Sci. of California, vol. iv. p. 182, pi. 1. fig. 7, 1871. 



Terebratella transversa, Dall, Proc. Acad. Nat. Sci. Philadelphia, 1873, p. 185. 



Terebratella occidentalis, Dall, Proc. Acad. Nat. Sci. Philadelphia, 1873, p. 181. 



