200 DE. T. DAVIDSON OX EECENT BEACHIOPODA. 



basis of the arms. The oesophagus passes obliquely through the tendinous wall of the 

 viscera in a direction towards the upper or imperforate valve; having then passed 

 between the anterior shell-muscles, it becomes slightly dilated and surrounded by the 

 liver, forming a less capacious stomach than in Terehratiila. The intestine is continued 

 straight to the opposite end of the visceral cavity, and is there again contracted, and 

 making a sudden bend upon itself, passes in a slight sigmoid curve to the middle of 

 the right side of the visceral belt, w'hich it perforates obliquely, and terminates between 

 the lobes of the mantle about half a line below the bend of the arm. The liver is of a 

 beautiful* green colour ; it is a congeries of elongated follicules closely compacted 



together, which communicate by numerous orifices with the stomach The coats 



of the stomach and intestines are thick and pulpy, and apparently glandular. Posterior 

 to the liver the whole of the visceral cavity not occupied by the muscles and vessels is 

 filled with grey masses of ova.'" Owen also detected traces of the nervous system. 



Prof. E. S. Morse states, in his paper on the systematic position of the Brachiopoda 

 (Proc. Boston Soc. Nat. Hist. vol. iv. 1873, p. 21), that Fritz Miiller has shown that in 

 the embryo of Discina there are remarkably barbed setae of great length, which are 

 afterwards discarded. The shell-structure of Discina is very similar to that of the genus 

 Lingnla, to which we have alluded under Liiigula anatina. That of Discina has been 

 carefully described by M. S. Cloez in the pages of the ' Institut,' p. 240, 1859, and is 

 also referred to by Dr. Gratiolet in his admirable memoir " Etudes anatomiques sur la 

 Litiffula anatina, Lamarck," Journal de Conchyliologie, vol. viii. 2" scr. 1860. 



110. DisciNiscA ATLANTiCA, King, sp. (Plate XXVI. figs. 18-22.) 



Discina atlantica, King, Proc. Nat. Hist. Soc. Dublin, vol. v. pp. 170-173, 1868. 



Discinisca atlantica, Dall, Cat. Recent Bracli., Proc. Acad. Nat. Sci. Pliiladclphia, p. 177, 1873. 



Discina atlantica, Jeffreys, Ann. &Mag. Nat. Hist. 4th ser. vol. xviii. p. 252, 1876, and Proc. Zool. Soc. 

 1878, p. 415 ; Davidson, Report on the Scientific Results of the Voyage of H.M.S. ' Challenger,' Zool. 

 vol. i. p. 62, 1880. 



Shell small, slightly oval longitudinally, broadest anteriorly, sometimes marginally 

 almost circular. Shell very thin, semitransparcnt, corneous, marked with numerous 

 concentric lines or ridges of growth. Upper valve conical; vertex situated at about 

 one third of the length of the valve from the posterior margin : ventral valve exceedingly 

 thin, fissure small, longitudinally oval. Colour light yellowish brown. Length and 

 breadth 2i lines, height 1\ lines. 



Hab. This small species was not known previous to 1862. Since then it has been 

 dredged in nine or ten separate and far distant localities. It appears to be a very 

 abundant shell, occurring only at very great depths. Prof. King, to whom we are 

 indebted for the first description and illustration of this interesting species, informs us 

 " that it was first dredged in 1862 by Staff-Commander Kichard Hoskyn, R.N., at the 

 time in command of H.M.S. ' Porcupine,' for purposes in connexion with the then- 

 proposed telegraphic connexion beti^ een Ireland and Newfoundland." The specimen 

 was not quite perfect, and " came up in the sounding-machine from a depth of 1210 

 fathoms, in lat. 52° 8' N., long. 15° 30', W., or nearly due west of Dingwall Bay." 



