232 Miscellaneous. 



retirugata) occur only in the Lower Purbeck ; and of the others, 

 six occur in both the Middle and Upper. Of the fourteen, five 

 ( Cypridea valdensis, \Qxy rare in the Purbeck, C. tuberculata, C. 

 DunJceri, Cyprione Bristovii, and Darivinula leguniinella) go up 

 into the Wealden from the Middle and Upper divisions only, Cy- 

 pridsa punctata iox ih.Q J] T^'^GT, G. granulosa ( fasciculata) for the 

 Middle, and Oypris purheckensis for the Lower Purbeck, seem to be 

 always characteristic. 



MISCELLANEOUS. 



On a new State of Rcticularian Rhizopods. 

 By M. DE FoLiN. 



Among the forms of Eeticularian Ehizopoda belonging to the tribe 

 Nuda, that is to say those which live without envelopes, we have 

 distinguished some remarkable examples formed by a sort of mem- 

 branous sheath, develoi^ng in tubes filled with sarcode. These 

 tubes present numerous branches, the interlacings of >vhich cross 

 one another upon several planes, giving to the whole the aspect of 

 an irregular network. These form the genus Fseudarhys. We 

 find them sheltered in all the cavities presented by old perforated 

 shells ; and from the mode in which they fill these and the multi- 

 plicity of branches of which they are composed, it might be sup- 

 posed that they had themselves hollowed out their shelters. Some 

 observations have shown us that this is not the case. One most 

 significant circumstance has just dissipated all doubts upon this 

 point, namely, the occurrence of a specimen of Pseudarkys inhabiting 

 the cells of a Dcntalina and adopting their form. It was very easily 

 distinguished through the semitransparent test, and in this position 

 it presented a clear proof that the organism certainly belonged to 

 the tribe Nuda. At its birth it had introduced itself into the 

 asylum, and in growing it had moulded its system of ramification 

 upon the inner walls. 



The same animal, varying in dimensions according to the retreats 

 in which it had taken up its abode, was met with in a considerable 

 number of the dredgings of the ' Travailleur ;' but the species seems 

 to remain the same. One of those of the 'Talisman,' on the other 

 hand, furnished us with an example of an alteration in the mode of 

 sheltering itself adopted by this organism. The branching, instead 

 of penetrating into a ready-made retreat, surrounded itself with 

 corpuscles, and esxiecially with Glohigerince, which were very abun- 

 dant on the bottom on which it lived. In some cases, the envelope 

 not being completed, it was easy to see how its constituents were 

 united and cemented by the sarcodesma. In this new condition a 

 mass of sarcode was nearly always accumulated, forming, in all 

 probability, a sort of reserve destined to become converted into 



