O. C. Marsh on the Remains of a new Enaliosaurian. 15 



seemed to indicate that a portion of it was of animal origin ; 

 and this has probably been preserved from the original substance 

 of the vertebrae. 



The estimation of the organic matter in many analyses of 

 fossil bones, which have been published, is based on the loss by 

 ignition. This method, if alone employed, as is usually the 

 case, is liable to give very erroneous results, especially where 

 the quantity of organic matter is small ; since the mineralizing 

 substances, introduced into the fossils by infiltration, not unfre- 

 quently may contain in close combination a considerable amount 

 of water, which remains at temperatures much above those ordi- 

 narily used in desiccation. Loss by ignition, therefore, in analyz- 

 ing such remains, is no proof of the presence of organic matter ; 

 and the results thus obtained are worthless in this respect, un- 

 less the existence of this substance has been otherwise ascer- 

 tained. The nature of the organic matter also should be deter- 

 mined ; as in animal remains from the older rocks it is occasion- 

 ally due to infiltration, and may be entirely of vegetable origin, 

 in the present analysis the "following method was employed 

 for the detection of the animal organic matter supposed to be 

 present in the fossils : A portion of the finely powdered mate- 

 rial, between one and two grammes in weight, was placed in a 

 beaker, and a small quantity of distilled water added ; the vessel 

 was then closely covered, and left on a sand bath where the tem- 

 perature was just suf&cient to cause a gentle ebullition. The 

 heat was continued, and the water renewed from time to time, 

 for several days, to effect the solution of any animal organic 

 matter the fossils might contain. The insoluble portion was 

 then filtered off, and the liquid evaporated to dryness in a plati- 

 num capsule, when the residue, on gentle ignition, carbonized, 

 and distinctly afforded the characteristic odor of burning nitro- 

 genous tissue. This, or some equivalent method of proving the 

 presence of animal organic substances, should always be em- 

 ployed in analyses of this kind, especially where a complete 

 separation of the organic ingredients is not attempted. 



A nitrogen determination was made on a portion of the ma- 

 terial somewhat different from that used in the preceding analy- 

 sis, and gave "776 per cent, for the amount of that substance in 

 the remains. This corresponds essentially with the results ob- 

 tained by M. Delesse, who has made somewhat extensive re- 

 searches on this point ; and who considers that the quantity of 

 nitrogen in fossil bones is, within certain limits, a reliable indi- 

 cation of their age.* The substance used in the above deter- 

 mination was evidently different from that previously employed ; 

 as the amount of nitrogen obtained would indicate a much larger 

 quantity of gelatigenous tissue than the analysis showed to be 

 » Comptes Rendus de I'Acad. dea Sci. de Paris, 1861, tome lii., p. 728. 



