252 On North-Atlantic BracMopoda. 



valves is not quite satisfactory, because the perfect specimen 

 is much more triangular and compressed, the beak more 

 pointed, and the foramen narrower than in the figures given 

 by Mr. Davidson. He could not, however, have done better 

 Avith the incomplete specimens which I had then placed in his 

 hands. 



Discina atlantica *, King. 

 Discina atlantica, King, Proc. Nat. -Hist. Soc. Dublin, 1868. 



Body semiglobose : arms furnished with very long and 

 slender setas or stiff hair-like cilia, which project beyond the 

 edge of the shell on every side to an extent fully equalling 

 its diameter : hifssiis cylindrical and narrow. 



Shell conical, more or less circular : upper valve umbrella- 

 shaped, thin, semitransparent, and rather glossy : scidpturty 

 numerous close-set and concentric minute striae or lines of 

 growth, which become somewhat irregular towards the outer 

 edge of tlie shell, and microscopically wrinkled lengthwise in 

 a radiating direction : colour pale brownish yellow : margins 

 thin and sharp : heak or apex very small, nipple-shaped, de- 

 pressed, placed nearer the dorsal margin : lower valve flat, 

 thin, having near its middle a comparatively small round disk, 

 within which is an oval slit for the passage of the byssal 

 stalk of attachment ; this disk is slightly sunk within any 

 calcareous substance to which it is attached, as if the byssus 

 had the power of excavation ; the rest of the lower valve is 

 free and concentrically striate, like the upper valve : muscular 

 (adductor) scars in the upper valve club-shaped, rather close 

 together ; no scars observable in the lower valve. Not the 

 slightest trace of a tubular or perforated structure could be 

 detected in either valve, with one of Smith and Beck's best 

 microscopes, under a lens of 3- power. L. 0'2, B. 0'2. 



Lat 5(3° ll'N.,long. 37°41'W., 1450 fathoms, Glohigerina- 

 ooze and stones (two living specimens and several upper 

 valves) ; lat. 56° 1' N., long. 34° 42' W., 690 fathoms, Glo~ 

 higeri'tia-oozfi. ' Porcupine Sounding,' 1862, 1240 fathoms 

 (Capt. Hoskyns) ; ' Porcupine' Expedition, 1869, 1366 fathoms 

 (J. G. J.) ; North-Atlantic sounding, while fishing up the 

 deep-sea telegraph cable, 2400 fathoms (Sir James Anderson). 



The surface of one of the upper valves dredged in 1450 

 fathoms exhibits the impressions or marks of two byssal disks, 

 by which other specimens had apparently been attached to it, 

 forming small circular shallow pits, with a deeper excavation 

 for the stalk or plug. The genus Discina^ of which the 



* Belonging to the Atlantic Ocean. 



