. The Cambridge natural history. Zoology. 282 REPTILIA families cannot well be changed, and terms like super-families and super-orders are sometimes resorted to by those who do not like to look stern facts in the face. The sequence of the groups, although arranged as much as possible in ascending order, is of necessity as unnatural as that of the maps in an atlas. We cannot yet construct a satisfactory phyletic tree of the Eeptiles. The Proreptilia connect them witli the Amphibia. Next follow the Prosauria with Sp]ienodo7i among the Prosauri as the key to most other groups. Then follow the The
. The Cambridge natural history. Zoology. 282 REPTILIA families cannot well be changed, and terms like super-families and super-orders are sometimes resorted to by those who do not like to look stern facts in the face. The sequence of the groups, although arranged as much as possible in ascending order, is of necessity as unnatural as that of the maps in an atlas. We cannot yet construct a satisfactory phyletic tree of the Eeptiles. The Proreptilia connect them witli the Amphibia. Next follow the Prosauria with Sp]ienodo7i among the Prosauri as the key to most other groups. Then follow the Theromorpha, and it is probable that from various branches of these have arisen the Chelonia, Dinosauria, Crocodilia, and Plesiosauria. The descent of the Ichthyosauria is very pro- blematic. The same applies to the Pterosauria and to the Pythonomorpha, but it is possible that they, together with the Sauria, are connected with the Prosauria. With all reserve these hypothetical affinities may be expressed by the following diagram :— Lacertilia ^Ophidia Ichthyosauria Plesiosauri, Sauria Chelonia. .Pterosauria Pythonomorpha Prosauria I Proreptilia The eleven sub-classes of the Eeptilia present so many important differences that it is not advisable to give here a further general account of their structure. The diagrammatic figures A' to T on pp. 280, 281, representing various types of skulls, are intended to explain their chief modifications, all referable to Proreptilian and to certain Theromorphous conditions. One of the most important features is that the mandible, which is always composed of many pieces (cf Pig. 142, p. 550), is invariably carried by the quadrate bone. Diagrams of the generalised skulls of a Bird and a Mammal have been added for comparison. As mentioned on p. 278 the vertebrae of the Eeptilia and those of all other Anmiota are gastrocentrous; that is to say. Please note that these images are extracted from scanned page images that may have been digitally enhance
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
