338 REPORT OF NATIONAL MUSEUM, 1897. 



Localities. — Coast of Yucatan, North Atlantic (stations 2358, 2530, 

 2614), 10 to 95G fathoms. 



POLYSTOMELLA CRISPA Linn^us. 

 (Plato 80, li<v. r>.) 



Lenticular, strongly biconvex, i)eripheral margin angular; sei)tal 

 pores in a single row, large, and closely set; umbilici filled with clear 

 shell-substance more or less porous. Diameter, about 0.7 mm. (i-- inch) 



Locality. — Not recorded. 



Subfamily ISTTTlMlVrTJT^ITIN".^. 



Test lenticular or coniplauate; lower forms with tlii(!kened and finely 

 tubulated shell- wall, but no intermediate skeleton; higher forms with 

 interseptal skeleton and complex canal system. 



Genus AMPHISTEGINA. 



Test spiral, lenticular, inequilateral; chambers equitant, the alar pro- 

 longations on one si<le simple, on tlie other divided by deep constric- 

 tions so as to form supplementary lobes. Shell- wall thickened near the 

 umbilicus and finely tubulated, but presenting no true canal system. 



AMPHISTEGINA LESSONII d'Orbigny. 

 (Plate 80, fig. 4.) 



Lenticular, somewhat unequally convex on the two sides; margin 

 angnlar; surface smooth; segments numerous, narrow, bent, simple on 

 the upper side, but constricted on the inferior side, and sharply bent 

 backward ; aperture on the under side of the last segment. Diameter, 

 about 1.5 mm. (-^g- inch). 



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

 tions 2415, 2029, 2641, 2363, 2370), 9 to 1,169 fathoms. 



