DESCRIPTIVE CATALOGUE OF RECENT FORAMINIFERA. 295 



Localities. — North Atlantic, Gulf of Mexico, and Panama Bay (sta- 

 tions 2530, 2883, 2399, 2805), 50 to 1,200 fathoms. 



BILOCULINA DEHISCENS, new species. 

 (Plate 40, fig. 3.) 



This species has the same general characters as B. depressa and its 

 variety serrata, but the last two chambers arc more or less separated at 

 the sides, giving the shell the appearance of rupture from internal 

 growth and distension. In general the separation is sufficient to show 

 the sharp edge of the third segment on each side, but series presenting 

 all degrees of gradation from Biloculina to Spiroloculina have been 

 selected from material dredged at a single station. 



Locality. — Gulf of Mexico (station 2377), 210 fathoms. (See Spiro- 

 loculina rouHsta, series.) 



BILOCULINA LiEVIS Defrance. 



(Plate 41, fig. 1.) 



Less compressed than B. depressa, less inflated than 7>. ringens; 

 characterized by the double border formed by the slight projection of 

 the margin of the penultimate segment. 



Locality.— Gulf of Mexico (station 2394), 420 fathoms. 



BILOCULINA SPHiERA d'Orbigny. 

 (Plate 41, fig. 2.) 



Specific characters well marked. Contour nearly spherical; each 

 chamber incloses the preceding one almost entirely, leaving exposed 

 only a small circular segment of the penultimate chamber. Aperture 

 an irregular, often branched or bordered, V-shaped slit. Section shows 

 arrangement of chambers and degree of investment. 



Localities. — North Atlantic, Gulf of Mexico, and coast of Brazil (sta- 

 tions 2352, 2385, 2415, 2754, 27G0), 440 to 1,000 fathoms. 



BILOCULINA IRREGULARIS d'Orbigny. 



(Plate 41, fig. 3.) 



Differs from other species of this genus in that it is compressed at 

 the sides instead of from above downward. Seen from above the con- 

 tour is oval; from the side the outline is broader, approaching the 

 circular when the compression is considerable. Aperture circular or 

 broad, with a valvular lip in the somewhat protuberant oral end. 



Localities. — Caribbean Sea and Gulf of Mexico (stations 2754, 2144, 

 2352, 2355, 2383, 2385, 2394), 400 to 1,200 fathoms. 



Genus SPIROLOCULINA. 



Chambers arranged in a single plane, the whole of them visible on 

 both sides of the shell. 



