260 Miscellaneous, 



temperature without perishing, there are cold-blooded animals that 

 can support and produce an elevation of temperature without danger 

 to their life. 



Some new members having been added to the commission, M. 

 Flourens took occasion to mention, that, along with M. Becquerei, he 

 had made some experiments on the temperature of cold-blooded ani- 

 mals. These experiments were made on several reptiles, on lizards, 

 serpents, Batrachians, &c., on several insects, and on some fish. The 

 temperature of all these animals was taken by comparative means, 

 namely, the thermo-electric apparatus of M. Becquerei and a very 

 delicate thermometer, so that the results obtained may be looked 

 upon as very exact. 



The most general result of these experiments is, that the animals 

 said to be cold-blooded have a temperature of their own, higher, that 

 is to say, than the external temperature ; so that they are really warm- 

 blooded animals. The temperature of lizards is more elevated than 

 that of the Batrachians, &c. A difference of temperature is even 

 found in the same animal, according to what region of the body is 

 examined : for example, the temperature of an adder is perceptibly 

 more elevated taken near the heart than it is in the region of the tail. 

 M. Flourens adds that M. Becquerei has long since committed the 

 physical part of this investigation to writing, and that he himself 

 will soon prepare the physiological part, and lay the entire memoir 

 before the Academy. — (LTnstitut, No. 424.) 



PALEONTOLOGY : RUDISTA. 



A memoir by M. Alcide d'Orbigny, entitled, " Quelques consi- 

 derations zoologiques et geologiques sur les Rudistes," read at the 

 Academy of Sciences Jan. 31, is published in the 'Ann. des Sc. 

 Naturelles' for March. It is summed up (LTnstitut, No. 424) in 

 the five following propositions : — 



1st. The Rudista hitherto unknown in the inferior districts of the 

 chalk formation, instead of being disseminated in the middle of the 

 terrestrial strata, form successive depots, banks whose horizon is in- 

 tersected; they may therefore be considered as the best marks 

 which can be taken as limits of strata. 



2nd. These distinct zones of Rudista, deposited in the middle of 

 the same basin and in a succession of strata but little dislocated, as 

 we see to the west of the Pyrensean cretaceous basin, might prove 

 that there was no need of great local disturbances to bring into the 

 same place difi^erent fauna ; but that, without doubt, other causes in- 

 fluenced this successive substitution of one fauna for another. 



3rd. The Rudista have appeared five times at the surface of the 

 globe in the cretaceous system, each time under entirely diflferent 

 forms, without there being any zoological passage in the species, or 

 transfer of individuals from one geological zone into another. Thus 

 the respective fauna of the five zones of Rudista, whether in distinct 

 stages, or in beds of the same stage, have been successively anni- 

 hilated and substituted by others wholly diflferent, which would not 

 evince in this series of beings any transition either of forms, or in 

 the beds which contain them. 



