No.n:t9. DKEI'-WATKIi MOI.LUSCAVERRILL AM) HUSH. S23 



Length of the largest specimens, 1.'! mm.; height, 10 nun.; breadth, 

 8 mm. 



Three specimens were found at three stations, off Marthas Vineyard, 

 in 100 to 115 fathoms, 1880-81. 



I'll is species resembles /'. nndulata in sculpture, but the latter is 

 narrower and longer in form, and has a more decidedly longer rostrum; 

 its chrondrophore is shorter and broader, and not so distinctly spoon- 

 shaped distally, while the marginal notch in front of it is relatively 

 much smaller. 



PERIPLOMA UNDULATA Yen-ill. 

 (I'lutes LXXIX, fig. 1; LXXXVII, fig. 5.) 



Pmploma nndiiht/a VERRILL, Trans. Conn. Acacl., VI, pp. 433, 448, 1885. 



A few specimens were found at six stations between N. hit. 39 9', 

 AY. long. 73 3' 15", and N. hit. 36 42', W. long. 74 30', in 541 to 810 

 fathoms, 1884-1887. 



Family LIMID^E. 



LIMATULA REGULARIS, new species. 



Shell small, thin, nearly equilateral, much higher than long, with 

 the hinge line straight and rather long. Umbos and median part of 

 the shell swollen. Beaks rather prominent, directly incurved. Liga- 

 ment al area relatively large, elongated, diamond-shaped, with the 

 pointed end extending nearly to the angles of the hinge-margin, with 

 a central, more sunken, short, rhomboidal ligament-pit which, on a 

 separate valve, forms nearly an equilateral triangle. The anterior and 

 posterior ends are nearly equally curved, a little convex, but slightly 

 narrowed where they join the hinge-margin and form a distinct obtuse 

 angle; on one side, supposed to be anterior, below the angle the mar- 

 gin is slightly incurved for a short distance, making this angle less 

 obtuse than the other. The ventral margin is nearly evenly rounded, 

 forming nearly the segment of a circle. The surface is covered with 

 small, elevated, radial ridges separated by concave grooves of greater 

 breadth; in the middle of the shell between ten and twelve of the 

 ridges are distinctly higher and thicker; on each side their size dimin- 

 ishes outwardly, so that near the angles of the hinge they become 

 nearly or quite obsolete, the last ones being mere raised, microscopic 

 threads; in some cases smaller ones alternate with the larger ones, so 

 that the total number can not be definitely determined, but fifty or 

 more can often be counted. There is often no very evident median 

 external sulcus, such as occurs in several related species, but the two 

 or three central radii are often, but not always, distinctly larger than 

 the rest. The radii are crossed by very tine lines of growth not suffi- 

 ciently strong to render them at all nodulose. The inner margin is 



