REPORT OF THE DIRECTOR I916 



115 



The Dipnoi contain : 

 Triassic — Recent Ceratodus 



The Teleostei: 



Cretaceous — Recent Diplomystus (in rivers of New South Wales 



and Chili) 



There are no persistent genera among the hatrachians, and none 

 among the reptiles save the turtle Chelone which ranges from 

 Cretaceous — Recent. 



No persistent genera, as here defined, are found among the birds 

 and mammals. 



In the following table we have compared the number of per- 

 sistent genera of each group cited in Zittel's textbook with the total 

 number of genera cited there, adding the percentage of persistent 

 genera : 



NUMBER OF 



PERSISTENT 



GENERA 



A 



Zittel- 

 East- 

 man 

 1896 



B 



Zittel- 

 East- 

 man 

 1913 



TOTAL 



NUMBER OF 



GENERA 



CITED 



PERCENTAGE 



A 



Foraminifera ...... 



Sponges 



Corals 



f Crinoidea . . . 

 Cystoidea . . 

 Blastoidea. . 

 Ophiuroidea . 

 Asteroidea . . 

 [ Echinoidea . 



Bryozoa 



Brachiopoda 



Pelecypoda . . . 

 Scaphopoda. . . 

 Gastropoda. . . 

 Pteropoda. . . . 

 Pulmonata. . . 



o rt 



.as 



29 



7 



42 



10 



I 



9 



46 

 5 



Cephalopoda 



Nautiloidea. . 

 Ammonoidea. 

 Dibranchiata . 



1 { Trilobita . 

 « S \ Ostracoda . . . 



u '^ ] Cirripedia . . . 

 ^ [ Malacostraca . 



Arachnida ^ 



Selachii 



Dipnoi 



Teleostei 



Reptilia 



49 



29 



71 



3 



108 



5 



8 



12 



7 

 16 

 5 

 9 

 3 

 16 



5 

 19 

 68 

 33 



78 



5 



126 



5 



7 

 12 



77 



90 



242 



169 



38 



23 



17 



32 



194 



225 



298 



452 



14 



376 



17 



67 



170 



455 



53 



45 

 20 



147 

 42 



168 



86 



149 



237 



277 



96 



23 



25 



43 



191 



306 



384 



446 



18 



420 



17 



65 



170 



455 



131 

 68 

 20 



134 

 66 



38 

 8 



17 

 6 

 3 



10 



'16 



4 

 21 

 10 

 15 

 21 

 29 

 29 

 12 



7 



13 

 35 



25 

 6 



7 



4-5 

 5 



38 



8 



17 



6.5 



IS 



14 



4.5 



IS 



IS 



14 



1 Including Merostomata. 



It is obvious that some of these figures are misleading in some 

 regards. They give a fair representation of the percentages in the 

 entirely or nearly extinct classes, while in those which are now 



