- calf
- callosity
- calluses
- Cambrian period
- canine
- cape
- carina
- carinate
- cariniform
- carnivores
- carnivorous
- carotenoid
- carrion
- cartilage
- castellate
- caudal
- cellulose
- Cenozoic
- centromere
- cephalopod
- cephalum
- character
- chelate
- chemistry
- chin
- chitin
- Chordata
- chorion
- chromatophore
- chromosome
- circumpolar
- clade
- cladogram
- clam
- cleptoparasitism
- cliff
- clines
- cloaca
- coastal
- coelom
- coitus
- colony
- columnar
- commensalism
- common
- competition
- concave
- condyle
- conical
- coniferous
- conspecific
- continental
- Continental shelf
- Continental slope
- convergence
- convex
- copepod
- copulation
- copulatory organ
- cordate
- corrugated
- cortical
- cosmopolitan
- countershading
- cow
- cranium
- crease
- crenulate
- Cretaceous
- cruciform
- Crustacea
- cuneiform
- currents
- curvilinear length
- cusp
- cutaneous