1936] Schults: Keys to Fishes 201 



Cycloid. Smooth-edged ; said of scales concentrically striate, with- 

 out any trace of minute spines. 



Deciduous. Temporary; falling off. 



Decurved. Curved downward. 



Dcntary. The anterior bone of the lower jaw or mandible, usually 

 bearing teeth. 



Dentition weak. Teeth scarcely evident. 



Dentition strong. Teeth very easily observed and highly developed. 



Denticle. A little tooth. 



Depressed. Flattened vertically, like the skates and rays. 



Depth. The vertical distance through the body at its deepest part, 

 not including the fins. 



Dermal. Pertaining to the skin. 



Diaphanous. Translucent. 



Disk (of skate). The more or less roundish body of the skate ex- 

 cluding the tail, ventral fins, claspers. The pectoral fins which 

 form a part of the body of the skate are a part of the disk. 



Distal. Remote from point of attachment. 



Dorsal. Pertaining to the back. 



Dorsal fin. The fin on the back, in front of the adipose if that is 

 present. In counting the fin rays, the anterior rudimentary 

 rays are omitted in certain groups of fishes such as Cyprinidae, 

 Catostomidae, Salmonidae, etc., or are given separately as sim- 

 ple rays in the following formula, 2 + 10, the simple rays be- 

 ing given first. Rudimentary rays are those rays, in general, at 

 the beginning of the fin which are unbranched, membraneless, 

 closely appressed the one to the other, and in ordinary cases 

 not more than half the length of the fully developed rays. The 

 last ray of the dorsal or anal fins is often split nearly or quite 

 to the base and appears as two rays, although counted as one. 

 In all cases, the last two rays are counted as one. In descrip- 

 tions, etc., Arabic numerals are used to indicate soft rays and 

 Roman numerals to indicate spines. A dash" — " separates ele- 

 ments not connected ; a comma those connected. 



Emarginate. Slightly forked or notched. 



Endoskeleton. The skeleton proper; the inner bony framework of 

 the body. 



Enteron. The alimentary canal. 



Epibranchials. The bones directly above the angle of the branchial 

 arches. 



Epihyal. One of the hyoid bones. 



Epipleurals. Rays of bone attached to the ribs and anterior verte- 

 brae. 



