DESCRIPTIVK CATAI.oraiE OF RECENT FORAMINIFERA. 271 



overlies the fiiiidameiital structure of sponge-spicules. Lenj^tli, 3 to 4 

 mm. (i to i inch). 



Localities. — Caribbean Sea, Gulf of Mexico, and oil Cape Fear (sta- 

 tions 2150, 2383, 2677), 382 to 1,181 fathoms. 



Genus RHABDAMMINA. 



Test rectilinear, radiate, or irregularly branching; with or without a 

 central chamber; the open ends of the tubes fornung the ai)ertures. 



RHABDAMMINA ABYSSORUM M. Sars. 

 (riate 12, tig. 2.) 



Test free, radiate, most commonly with three rays in the same plane, 

 but occasionally with four or live or more rays sometimes projecting 

 irregularly from the central body; walls thin; central chamber small; 

 the tubular arms terminating in simple rounded apertures. The speci- 

 mens exhibited are below the av^erage in size, but were selected for con- 

 venience of mounting. Section shows the form of the cavity, and 

 thickness of the walls. 



Locality, — Gulf of Mexico (station 2383), 1,181 fathoms. 



RHABDAMMINA DISCRETA Brady. 

 (Plate 13.) 



Test in the form of a long, straight cyhnder, slightly constricted at 

 irregular intervals and open at both ends; cavity smooth; walls rather 

 thin, constructed of coarse sand firmly cemented. Sometimes reaches 

 a length of an inch or more. 



Locality. — Off Chesapeake Bay (station 2731), 781 fathoms. 



RHABDAMMINA LINEARIS Brady. 

 (Plate 14, fig. 1.) 



Test free, long, straight or slightly bent, cylindrical, having an oval, 

 inrtated central chamber with two long arms projecting in opposite 

 directions on the same linej tubular portion slightly tapering; walls 

 vary in texture from very fine sand mixed with sponge-spicules to (^uite 

 coarse angular sand grains; cavity corresponds to the outward form of 

 the test; apertures simple, one at each end. Length, 3 to 12 mm. (^ to 

 i inch). 



Localities. — Off' Georges Bank, and off the coast of Brazil (stations 

 2570, 2760), 1,019 and 1 ,813 fathoms. 



RHABDAMMINA CORNUTA Brady. 

 (Plate 14, fig. 2.) 



Test free, asj^mmetrical, consisting of an inflated chamber of irregu- 

 lar contour, and numerous short arms radiating from the surface; walls 

 thin, composed of a single layer of rather coarse grains of white sand. 



