PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 35 Z 



In the Equulids, among^ others, the extension is in the region just 

 behind the cranium or about the nape, and hence such may be called 

 nuchadiform. 



In the Patsecids the extension is to the direction of the front of the 

 head, and a frontadiform outline results. 



III. 



In certain other types it is the iriferior region that is expanded. 



In the Sternoptychids the extension is downwards in front of the anal 

 region ; the resulting shajje is the ventradiform. 



In the Zenids and Gerrids the tendency of expansion is about the 

 thoracic region ; it may (taking advantage of a frequently used analogy) 

 be designated the sternadiform. 



IV. 



Certain other forms do not manifest any decided deviation one way 

 or another in a vertical direction. 



The CentrarchidSj Cichlids, Labrids, Pimelepterids (or Cyphosids, if 

 it is deemed best), and many others have the dorsal and inferior out- 

 lines almost exactly inverted, so that, if the body (exclusive of head) 

 could be simply folded lengthwise, the two margins would be found to 

 be nearly coincident. The shape thus constituted may be designated 

 antadiform. 



In the Chaetodontids, an apparent expansion is manifested by the 

 encroachment of the skin and scales on the soft dorsal and anal fins, 

 and they may be distinguished as innnadiform. 



In many fishes, such as the Coryph8eni<ls, Uranoscopids, Batrachids, 

 Triglids, &c., the body regularly inci eases in height or vertical exten- 

 sion towards the head, and they are consequently antrorsiform. 



In Lampris, the height is greatest considerably in advance of the 

 middle, apd hence an oviform outline ensues. 



In the Trichiurids and some others the body is much elongated and 

 greatly compressed, and they have quite generally and appropriately 

 been called tceniiform or ribbon-shaped. 



V. 



Some exceptional deviations are manifested by very different forms. 



The Toxotids and Amphisilids are both distinguished by a sort of de- 

 pression or flattening of the dorsal outline from the head backwards 

 to the dorsal fin. Tlie name retradiform may be used to express this 



feature. 



VI. 



Other names, derived from special types, may be used inasmuch as 

 they already have some currency and are not apt to produce much 

 misconception. Such are anguilUform^ platessiform^ soleiform, sqiiali- 

 Jorm, &c. 



