384 VERTEBRATE ANIMALS OF THE UNITED STATES 



Cranial crests. A pair of longitudinal ridges between the eyes on the head of toads. 



Cranium. The portion of the skull which encloses the brain. 



Cruciform. Cross-shaped. 



Ctenoid. Fish scales which have a pectinated or roughened posterior margin. 



Cusp. A sharp projection. 



Cuspidate. Ending in one or more sharp points. 



Cycloid. Fish scales which have a smooth posterior margin. 



Cyclostomate. Round-mouthed; a group of primitive fish-like vertebrates. 



Deciduous. Temporary; characterized by falling off at a certain time. 



Decurved. Curved downwards. 



Dentate. Notched. 



Dentine. The very hard, inner substance of a tooth; ivory. 



Dentition. The number of each of the four kinds of teeth of a mammal. 



Depressed. Flattened dorso-ventrally. 



Depth. The dorso-ventral height of a fish's body at the widest place. 



Dermal. Arising in the dermis of the skin. 



Dermis. The inner layer of the vertebrate skin or integument. 



Dextral. Pertaining to or situated on or towards the right hand. 



Diaphragm. The muscular septum between the thoracic and abdominal cavities in 



mammals. 

 Dicromatic. Two-colored; applied to animals having two color phases. 

 Digit. A finger or toe. 



Digitigrade. Walking on the toes instead of on the flat of the foot. 

 Dimorphic. Characterized by dimorphism. 

 Dimorphism. Existing in two distinct forms. 



Distal. .\way from the point of attachment; opposed to proximal. 

 Diurnal. Appearing or active during the day. 

 Diverticulimi. A sac-like projection of a tubular organ. 

 Dorsal. Pertaining to the back. 



Dorsal fin. The median fin on the back of a fish or amphibian. 

 Dorsals. The median plates of a turtle's carapace. 



Dorso-lateral ridges. A pair of glandular ridges on the back of most frogs. 

 Ear -ossicles. The three minute bones in the middle ear of mammals. 

 Ecru. Cofi'ee-color. 



Ectoderm. The outermost layer of cells in the body of an embryo. 

 Elaphine snakes. Snakes which have a pair of short rigid poison fangs in the front of the 



upper jaw. 

 Elasmobranch fishes. Sharks and skates. 

 Emarginate. Slightly forked or notched. 

 Embryo. A young animal which is passing through its developmental stages, usually 



within the egg-membranes or in the maternal uterus. 

 Enamel. The very hard outer covering of a tooth. 



Endoskeleton. The inner bony or cartilaginous framework of the body. 

 Entire. Xot divided or split. 

 Entoderm. The embryonic cell layer which forms the mucous membrane of the digestive 



tract. 

 Epidermal. Arising in the epidermis of the skin. 

 Epidermis. The outer layer of the vertebrate skin or integument. 

 Eustachian tube. A canal joining the middle ear with the pharynx. 

 Exoskeleton. The hard parts, as the nails, scales, feathers, hair, etc., on the outer surface 



of the body. 

 Extremities. The paired locomotory appendages of the body, as the legs, wings, etc. 

 Falcate. Scythe-shaped; elongate, slender and curved. 



