1888.] 



A new Form of Eudiometer, 



383 



united by suture to the coracoid. The inter-clavicle had the slender 

 ~|~-shaped form of the bone in Ichthyosaurus. 



Procolophon has teeth on the vomera and pterygoid bones, and the 

 structure of the palate and the post-orbital region show that the 

 Procolophonia forms a distinct division of the Anomodontia. Obser- 

 vations are made on the relations of the European and South African 

 Anomodonts, and on the relation of the Anomodontia to the Pelyco- 

 sauria and to Cotylosauria. Comparison is made with Placodus, 

 which genus has two exoccipital condyles, comparable to those of 

 mammals, and appears to have lost the basi-occipital condyle. Com- 

 parisons are made with other extinct reptilia to show the relation of 

 the Anomodonts to the Saurischia, and other reptilian types. Obser- 

 vations are offered on the theory of the Anomodont skull, and on the 

 effect of the articulation of the lower jaw with the squamosal in 

 causing a diminished growth of the malleus and quadrate, converting 

 them into the malleus and tympanic. 



The larger groups included in the Anomodont alliance are regarded 

 as the Pareiasauria and Procolophonia ; Dicynodontia, Gennetotheria, 

 aud Pelycosauria ; the Theriodontia, Cotylosauria, and Placodontia 

 are regarded as coming under the same sub-class, which at one end of 

 the series exhibits characters which link reptiles with amphibians, 

 and at the other end of the series link reptiles with mammals. 



XII. "A new Form of Eudiometer." By William IlARCET, 

 H.D., F.R.S. Received June^O, 1888. 

 [Plate 14.] 



The quantitative determination of oxygen, simple as it appears at 

 first sight, is found in practice beset with many difficulties. Liebig's 

 method with pjrogallic acid and potassium hydrate, though con- 

 sidered as yielding correct results, takes too much time, and is un- 

 satisfactory in some respects, so that the eudiometer has become of 

 general use for the estimation of oxygen. I shall not attempt to 

 describe the various forms of eudiometer, but it may be assumed that 

 Regnault, so well known for the care he bestowed on his investiga- 

 tions, had adopted a very correct kind of eudiometer in the researches 

 he undertook with Reiset on the chemical phenomena of respiration.* 

 Other eudiometers have been made since then, such as the ingenious 

 instrument of Dr. Frankland for gas analysis, which has proved most 

 serviceable. I claim for the present form of eudiometer that it is 

 correct and reliable in its working, simple in construction, and easy 

 of manipulation. The main objects of an eudiometer must be the easy 

 introduction of the air to be analysed, the ready mixture of that air 

 with a known volume of pure hydrogen gas, and the correct reading 

 * ' Annales de Chiroie et de Physique,' 3rd Series, vol. 26, 1849. 



