FORAMINIFERA OF THE ATLANTIC OCEAN 



13 



Genotype, by designation. — Discorbis i^esicularis Lamarck. 



Test typically plano-convex, the ventral side flattened, early por- 

 tion sometimes showing a long Spirillina-\ike second chamber before 

 division; chambers often produced to partially cover the umbilical 

 area; wall calcareous, perforate; aperture at the base of the umbilical 

 margin on the ventral side of the chamber. 



Lower Cretaceous to Recent. 



Discorbis is a simple genus, in many of its species showing consid- 

 erable complexity, but tj'^pically the species have a depressed umbilicus 

 although sometimes covered by ingrowing portions of the chambers. 

 The aperture is in the general umbilical region or at the base of the 

 chamber near it. Som_e of the Indo-Pacific species become much 

 ornate and highly developed while most of those of cool waters are 

 fairly simple in form and structure. 



There are so many specific names used here that they are arranged 

 alphabetically for easier reference. 



DISCORBIS ADVENA Cushman 



Plate 2, figures 8 a-c 



Discorbina rosacea H. B. Brady (part) (not d'Orbigny), Rep. Voy. Chal- 

 lenger, Zoology, vol. 9, 18S4, p. 644, pi. 87, fig. 1.— Flint, Rep. U. S. 

 Nat. Mus., 1897 (1899), p. 327, pi. 72, fig. 3. 



Discorbis advena Cushman, Publ. 311, Carnegie Instit. Washington, 1922, 

 p. 40. 



Test rotaliform, dorsally convex, ventrally concave, composed of 

 numerous chambers, usually 6 in the last-formed coil, distinct, the 

 periphery rounded in the final chambers, earlier development with 

 a rather acute edge; sutures distinct, very slightly depressed, oblique; 

 wall thin, translucent, very finely perforate; on the ventral side the 

 test is umbilicate, the chambers ending in a peculiar inflated point; 

 aperture a very narrow, slightly curved opening at the base of the 

 inner margin of the last-formed chamber. 



Diameter up to 0.50 mm. 



Discorbis advena — Material examined 



Cat. 



No. 



2667 

 2665 

 2660 

 2661 



Collec- 

 tion of— 



J.A 

 J.A, 

 J.A 



J.A, 



2664 I J.A, 



2658 J.A, 

 2663 J.A. 

 2657 J.A. 

 2666 ! J.A 



2659 ' 

 2656 

 2668 

 2662 



J.A, 

 J.A 

 J.A, 

 J.A 



Locality 



Dry Tortugas, Fla. 



do 



do 



do - 



do 



.do 



.do 



.do 



.do -. 



.do 



.do -. 



.do 



.do 



Depth 

 in 



fath- 

 oms 



1 



11 



7 

 12 



5.75 



7 



7 



10.5 



7 



4.75 

 11 



Bot- 

 tom 

 tem- 

 pera- 

 ture 



Character of 

 bottom 



dead coral.. 



s 



hrd. bot 



fne. s 



fne. s 



fne. s 



fne. s 



fne. s 



fne. s - 



m. S- 



fne. m. s 



fne. s.- , 



fne. s 



Abundance 



Rare. 



Do. 



Do. 



Do. 



Do. 

 Few. 



Do. 

 Rare. 



Do. 

 Few. 

 Rare. 

 Few. 



Do. 



