52 THE VOYAGE OF H.M.S. CHALLENGER. 



6. Bairdia formosa, G. S. Brady (PI. X. fig. 1, c^-e). 



Bairdia foi-mosa, Brady, Ann. and Mag. Nat. Hist., 1868, ser. 4, vol. ii. p. 221, pi. xiv. figs. 5-7. 



Carapace as seen from the side subtriangular, all the angles broadly rounded ofi", 

 height greatest in the middle, and equal to three-fourths of the length ; the dorsal 

 margin is excessively arched, and somewhat gibbous in the middle, the ventral straight 

 or rather convex ; anterior extremity broadly rounded, posterior narrower, slightly 

 produced below the middle ; seen from above, the outline is very broadly ovate, the 

 greatest width being situated in the middle, and equal to more than haK the length ; 

 extremities obtuse, submucronate ; the end view is broadly ovate, the height considerably 

 greater than the width. In well-developed adult specimens the surface is shghtly 

 punctate, and is beset with numerous slight tubercular or papilliform eminences, the left 

 valve bearing also at its infero-posteal angle a series of five or six spines ; the right 

 valve is fringed along its anterior margin with a considerable number — twelve or more — 

 of small blunt teeth ; young specimens have the shell quite smooth and destitute of 

 marginal teeth. Length, 1-1 6th of an inch (1"55 mm.). 



Numerous specimens, chiefly detached valves, of this handsome species occurred in 

 dredgings from lat. 38° 11' N., long. 27° 9' W., 900 fathoms, on a bottom of globigerina 

 ooze (Station 76) ; from lat. 8° 37' S., long. 34° 28' W., 675 fathoms, muddy bottom 

 (Station 120) ; from a depth of 350 fathoms ofi" North Brazil, lat. 9° 5' S., long. 34° 49' 

 W. (Station 122) ; and (one or two doubtful examples) from lat. 5° 26' S., long. 133° 19' 

 E., 580 fathoms (Station 191a). 



The Mediterranean sj)eciniens from which Bairdia formosa was originally described, 

 differ not inconsiderably from those now under notice, being rather more elongated, more 

 distinctly beaked behind, sharper and more constant in theu' spinous armature, and in 

 the pitting of the shell surface. But notwithstanding this, the general aspect is so 

 similar that I think it quite reasonable to look ujDon the specimens from these various 

 localities as specifically identical. At any rate it would not be easy to point out good 

 characters for specific distinction. 



[PL X. fig. 1 , a-e. a Carapace seen from left side, h from right side, c from above, d 

 from below, e from front. Magnified 40 diameters.] 



7. Bairdia ahjssicola, n. sp. (PI. VIL fig. 4, a-c). 



Left valve, seen laterally, subreniform, highest in the middle ; height equal to about 

 two-thirds of the length ; anterior extremity broadly rounded, posterior somewhat pro- 

 duced and narrowed, dorsal margin boldly arched, ventral nearly straight. The right 

 valve is narrower, more produced behind, and has the dorsal margin sinuated near 

 the front. Seen from above, the outline is regularly ovate. Surface of the shell quite 

 smooth. Length, 1-1 6th of an inch (1'55 mm.). 



