280 PAL.EONTOD N ! V 



that time ; whilst the tailless genera and species are most 

 numerous and various at the present day. The Ophidia 

 resemble the Anoura, commencing in the older tertiary, and 

 showing their maximum of development at the present day. 

 The true proccelian, and especially the pleurodont, lizards, 

 commencing a little earlier in the chalk, have also gone on 

 increasing in number and variety of forms to the present day. 

 The acrodont group was represented by Mosasaurus, with a 

 maximum of size, during the cretaceous period. The Theco- 

 donts have but the partial relationship to modern Laccrtilia 

 which the Labyrinthodonts bear to the modern Batrachia. 

 The great ordinal groups of Ielithyo- and Sauro-pterygia, <>f 

 Pterosauria, and Dinosauria, together with the amphi- and 

 opistho-ccelian Crocodilia, passed away ere the tertiary time 

 had dawned. The proccelian crocodiles which culminated in 

 the lower and middle tertiary times, are now on the wane. 

 Perhaps, also, the same might be said of the Chelonia, in 

 regard to the size of individuals and the number of species of 

 certain genera {e.g. Chelone, Trionyx, Chelydra). 



Class III.— AVE S. 



Long before any evidence of birds from actual or recog- 

 nizable fossil remains is obtained in tracing the progress of 

 life from the oldest fossiliferous deposits upwards, we meet 

 with indications of their existence impressed in sandstones of 

 the triassic or liassic period. 



These earliest evidences of the class are by footprints in 

 some former tidal shore, preserved in one or other of tin 1 ways 

 explained in the section " Ichnology." The fossil bones of 

 birds have not been found save in strata of much Inter date 

 than the impressed sandstones ; and they are much more rare 

 than the remains of mammals, reptiles, and fishes, in any 

 formations except the most recent in certain Limited Localities, 

 — e.g., New Zealand. 



