NOTES ON RETICULARIAN RHIZOPODA. S83 



and further that they do not reach the entire width of the test, 

 but are laid on alternately. In other words, that the shell 

 begins growth as a Textularia, and subsequently constructs 

 a single series of large, flat, arched segments, which give it 

 its fan-like contour. The shell-wall is thin and transparent, 

 the perforations numerous and large, and the sutures limbate. 

 The general aperture takes the form of a row of small orifices 

 on the outer face of the terminal segment. The diameter of 

 the largest specimen which has been found is ^W inch 

 (about 1*0 millim.). 



Paxonina JiaheUiformis has been taken at three of the 

 " Challenger " stations, namely, Nares Harbour, Admiralty 

 Islands, 17 fathoms; off Culebra Island, "West Indies, 390 

 fathoms ; and off the reefs, Honolulu, 40 fathoms. These, 

 with the habitats furnished by the researches of d'Orbigny 

 and the material collected by Dr. Perceval Wright, represent 

 our knowledge of the distribution of the species. 



G'eww^— PLANORBULINA, d'Orligny, 



Planorbulina echinata, 71. sp. PI. VIII, fig. 31, a, h, c. 



Characters. — Test nearly spherical ; composed of few seg- 

 ments, about four in the last convolution. Segments ven- 

 tricose, unequally arched, embracing. Shell coarsely perfo- 

 rated and usually armed externally with short, blunt spines. 

 Aperture large, round, sometimes partially closed by a 

 shelly plate within the bordering lip. Diameter ttV inch 

 (0-32 millim.). 



The affinity of this little organism to the HotalincR is 

 easily determined, notwithstanding its anomalous shape; and 

 the bordered neck which forms the aperture, together with 

 the coarse perforation of the shell-wall, suggest its more 

 intimate connection with the genus Planorbulina. It is a 

 minute, inconspicuous species, and cannot well be confounded 

 with any previously known. 



Planorhulina echinata has its home amongst the coralline 

 sands of shallow seas, and has been found at ten or twelve 

 of the "Challenger" stations, chiefly amongst the islands of 

 the Pacific, Except in one locality, Nares Harbour just 

 south of the Equator, the number of specimens from any 

 single habitat is very small. 



