NOTES ON RETICULAKIAN RHIZOPODA. 31 



parative absence of any kind of cement or other incorporating 

 medium for the extraneous matters which are used in forming 

 its walls. Hence the test is soft and cruinbling and the 

 requisite strength is obtained by increased thickness^ and 

 it is never compact, enough in texture to be spoken of as a 

 " shell.'' 



What the precise nature of the membranous tubular 

 prolongations of the test may be, whether they are part of a 

 definite chitinous envelope or merely the superficial portion 

 of the sarcode in a somewhat altered condition, has not been 

 satisfactorily determined. The genus Astrorhiza again 

 furnishes us with the nearest parallel. The specimen of 

 A.. conz2^^a (PI. IV, fig. 15) has tubular membranous extensions 

 from the ends of the branches, not always simple, as in 

 Pelositia, but usually bifurcating ; and in a large undescribed 

 species of the former genus of which I have a specimen, 

 dredged by Mr. F. M. Balfour in the North Sea, a con- 

 siderable portion of the body of the animal has a membranous 

 investment, only slightly sprinkled with sand-grains or mud. 

 These facts tend to indicate that Pelosina should have a 

 place very near to Astrorhiza in the zoological series. 



The best specimens of Pelosina variabilis amongst the 

 " Challenger" deep-sea spoils are from a sounding on the east 

 side of New Zealand, in 1100 fathoms, but single specimens 

 have been met with in several other localities. 



Pelosina rotundata, n. sp. PI. Ill, figs. 4, 5. 



Characters. — Test consisting of a single flask-shaped or 

 pyriform chamber, with produced membranous neck. Walls 

 thick composed of muddy Glohigeri7ia- ooze. Diameter, tt^^ 

 inch, (2 millim.). 



This species differs from P. variabilis, in that it consists 

 uniformly of a single subglobular or pyriform chamber, and 

 that it is usually of smaller dimensions. The walls are rela- 

 tively very thick, and are composed of soft, greyish-white, 

 muddy material, with scarcely any incorporating cement. It 

 naturally follows that the central cavity occupies but a very 

 small proportion of the entire bulk of the test. 



Pelositia rotundata appears to be essentially a North 

 Atlantic species. Amongst the " Challenger" dredgings I 

 have only found it from one station, namely, off the Azores, 

 in 1675 fathoms, but it occurs in one of the " Porcupine" 

 soundings in much shallower water, 109 fathoms. 



