ORDERS. 45 



5. BRAKCHJOSTEGUS, skeleton cartilaginous ^ 

 without ribs ; having gill membranes ; with or 

 without gill-covers. 



Examples. Sucker, mullet, sun-fish, 



6. CHONDROPTERYGIOUS, skeleton cartilagen- 

 ous> without ribs ; gill- membranes wanting ; with 

 vr without gill- cover $. 



Examples. Lamprey, ray, shark, sturgeon, 



V. CLASS ANNELIDA 



IS DIVIDED INTO THREE ORDERS. 



1. TUBICOLA, articulated, semi-mdluseous ani- 

 vials, with red blood, encased in calcareous tubes. 



Examples. Serpula or sea-pipe, arnphitrite, 

 tooth-shell or dentalium. 



2. DORSIBRANCHIA, back-gilled. Their respira- 

 tory organs are distributed all along the body to- 

 wards one side, called the back, 



Examples. Nereis, aphrodite. 



3. ABRANCHIA, having no gills or other respira- 

 tory organs ; but their respiration is performed by 

 the entire surface of the skin. 



Examples. Angle-worm, leech or blood-suck- 

 er, nais, gordius or hair snake. 



VJ. CLASS CRUSTACEA 



IS DIVIDED INTO FIVE ORDERS. 



t. DECAPODIA, ten footed. Head confounded 

 with the trum ; eyes movvable ; mandibles with 

 palpi or feelers* 



The gills are situated at the outer base of the 

 feet* A numerous order. 



Example. Crabs, lobsters. 



