824 PROCEEDINGS OF THE NATIONAL MUSEUM. voi.xx. 



distinctly creimlated along the prominent ventral edge, tbe crenula- 

 tions corresponding to tbe external grooves and ridges, but at the ends 

 it is smooth. There is often a distinct, median internal groove, extend- 

 ing from near the beak to the middle of the ventral margin, bordered 

 on each side by a distinct raised ridge, sometimes having an additional 

 groove on their outer sides. The hinge-margin is rather thin, nearly 

 straight, and a little excavated or incurved along the ligamental pit; on 

 each side and considerably within the margin there is a small triangular 

 buttress or shelf-like process extending to the anterior and posterior 

 margins as in the allied species, but rather larger than usual. 



Length of one of the largest species, 6 mm. ; height, 9.0 mm. ; thick- 

 ness, about 5 mm.; length of hinge-margin, 3.6 mm. 



A number of separate valves, station 2265, N. lat. 37 7' 40", W. 

 long. 74 35' 40", in 70 fathoms, 1884. 



This species is allied to Limatula subonata (Jeffreys) Smith, 1 which 

 is distinguished by its shorter hinge-margin, more contracted form, 

 with stronger and higher radial ribs and well-marked median sulcus. 

 It also lacks the incurvature of the margins below the angles of the 

 hinge. 



LIMATULA NODULOSA, new species. 



Shell small, nearly equilateral, vertically ovate, narrowed above, with 

 a comparatively short, straight, hinge-margin. Umbos prominent, a 

 little compressed. Beaks small, a little prominent, directly incurved. 

 Surface covered with radial ribs which are very fine and even on the 

 anterior and posterior ends, but in the middle region, become much 

 stronger and are rendered nodulose by strongly marked, raised, concen- 

 tric lines and grooves. The two median ones are much stronger than 

 the others and are separated by a distinct median sulcus. The inner 

 surface is marked by radial ridges and grooves of which the median ones 

 are much the stronger; inner margin crenulated ventrally by the ends 

 of the ribs and grooves. Ligamental area diamond shape with a small, 

 short, rhomboidal ligament-pit in the middle. The hinge-margin forms 

 an obtuse angle at each end, the two nearly or quite equal; internal 

 buttress well developed with the inner margin regularly curved and 

 continuous across the middle, so as to thicken the hinge in this part. 



Length, 4.5 mm.; height, 7 mm.; thickness, about 4 mm.; length of 

 the hinge-margin, 2 mm. 



A single valve, among Foraminifera, at station 2385, 1ST. lat. 28 51', 

 W. long. 88 18', in 730 fathoms, 1885. 



This species agrees with L. subovata (Jeffreys) Smith almost com- 

 pletely in size and form, but differs very decidedly in the strong, nodu 

 lose, radial ribs which cover the middle portion of the shell. 



1 Limci'a subovata Verrill, Notice of Keceiit Add. to Mar. Invert., Ft. 2, Proc. U. S. 

 Nat. Mus., Ill, p. 402, 1881. 



