26 FISHES OF NORTH CAROLINA. 



use of the work in identifying the species; the diagnoses have likewise been made 

 as brief as is consistent with this purpose and have been based almost exclusively 

 on external characters. A free translation of the meaning of all the generic and 

 specific names has been given.* 



THE CLASSES OF FISHES AND FISH-LIKE ANIMALS. 



The creatures popularly called fishes belong in three great classes, which 

 may be distinguished by the following characters. The first two classes are 

 quite unimportant in the present connection, each having only a single representa- 

 tive in the state; and only the last class contains the fishes properly speaking. 



Key to the classes of fishes and fishAike animals, 

 i. Animals with cartUagiaous skeleton and without brain or skull; fins rudimentary and only on 

 median line of body; mouth a slit surrounded by bristles; heart a tubular vessel without 

 separate chambers; blood colorless; gill-slits numerous, the respiratory cavity opening 

 into the abdomen; inspired water discharged through a special abdominal pore. 



Lbptocardii (lancelets). 



ii. Animals with cartilaginous or bony skeleton; skull and brain present; heart developed as a 



cavity with at least two chambers; blood red. 



a. Eel-shaped; skeleton cartilaginous; skuU imperfect; mouth circular, suctorial; no jaws 



or paired fins; a single median nostril; gills pouch-shaped and numerous; skin naked; 



alimentary canal straight, without coeca; pancreas and spleen absent. 



Maesipobeanchii (lampreys, etc.). 

 aa. Skull well-developed; jaws distinct; fins usually highly-developed, some of them paired; 

 skin usually scaly; nostrils at least two, not median; gill-openings a single slit on each 

 side in most fishes (numerous in a few families); alimentary canal more or less con- 

 voluted; pancreas and spleen present Pisces (fishes). 



* Following is an explanation of some of the arbitrary features adopted in describing the species: 

 In the statement of the general shape of a species the relation of the depth and fhe length of head to the 

 length is given. By depth is understood the greatest vertical diameter of the body, while length or total length 

 means the distance in a straight line from the end of snout to end of the backbone, or, what usually amounts 

 to practically the same thing, to the base of the caudal fin; the length of head is the distance in a straight line 

 from the end of snout to the most posterior part of the gill-cover. The relative size of parts may vary with 

 the size, age, sex, and spawning condition of the individual; and the figures given in the diagnoses must be 

 regarded as simply averages for adult fishes. In the young, the head and eye are usually larger, the depth less 

 and the mouth smaller than in mature examples. 



In noting the fin formulae, spinous rays are always recorded with Roman numerals and soft rays with 

 Arabic figures. Thus, '*dorsal rays 10" means that a fish has a single dorsal fin with 10 soft rays; "dorsal rays 

 IV. 10" means that a fish has a continuous dorsal fin composed of 4 spines aad 10 soft rays; "dorsal rays iv + 

 10" means that a fish has two separate dorsal fins, the anterior with 4 spines and the posterior with 10 soft rays; 

 and ' dorsal rays lll + l, 10" means that a fish has two separate dorsal fins, the anterior with 3 spines and the 

 posterior with 10 rays preceded by a single spine. 



The number of scales in lateral series is usually computed along the lateral line, and often corresponds 

 with the number of pores or tubes in the lateral line: when the lateral line is absent or incomplete, the count is 

 made from the gill-opening to the base of the caudal fin. The number of scales in crosswise series is determined 

 by counting an oblique row from the base of dorsal fin to the lateral ling and from the lateral line to the base 

 of anal fin or to the vent 



