61 



and 400 are terrestrial and air-breathers. They are distributed among 

 the classes as follows : 



Cephalopoda 25 



pulmonata 400 



! Fresh-water 438 



Marine 297 



28 



Heteropoda . . 

 Opisthobranchiata 



Pteropoda 



scaphopoda 



Lamellibranchiata 



Fresh- water. 

 Marine 



. 53 



25 



4 



596 



377 



10 



30 



Bryozoa 39 



The remaining divisions of the animal kingdom may be estimated to 

 number nearly as follows: 



MOLLUSCOIDA. 



Braohiopoda . 



ASCLDIA .,.-.. 



ECHINODERMATA (123), 



HOLOTHURroA. 

 ECHINOIDEA . . . 



Crinoidea 



asteroidea.. 



Medusae : 



Discophora . . 



Siplionophora 



Ctenophora 



Polypi 



Hydroidea 



Coelenterata (144). 



The divisions of Protozoa are well represented in our waters, but the 

 numbers of our Spongiida, Infusoria and Rhizopoda, have not vet 

 been avscertaiued. 



III. — RELATIONS TO OTHER REALMS. 



It bas been already remarked that several species of Vertehrata are 

 common to our northern regions and Europe, Asia, etc. Thus, the 



