THE SHORE FISHES OF PERU 7 



characters used in the descriptions is fairly vuniform. That is, the 

 various characters commonly described, if mentioned at all, are named 

 in the same order in all the descriptions. In general, the shape of the 

 body is mentioned first. Next, the head is described; then the charac- 

 ters about the head, such as the snout, eye, interorbital, mouth, teeth, 

 and gill rakers, are defined. Next, the lateral line, the scales, the fins, 

 and finally the color are described. This uniform sequence was 

 carried out for the convenience of the student, who in using the catalog 

 should soon learn where to look for the description of any particular 

 character he may wish to check. 



Specimens examined. — The number and size of the specimens of each 

 species used in preparing the descriptions invariably have been stated. 

 It seemed desirable to give this mformation, as the student thereby, 

 in a measure at least, may judge the value of the variations given, for 

 obviously small or large specimens alone of any one species will not 

 show the usual variations within that species. Nor will a few speci- 

 mens, regardless of size, provide so true a range of variations as a large 

 series of various lengths. 



Measurements, proportions, abbreviations, and enumerations. — The 

 proportions used in the descriptions were obtained by making all 

 measurements with vernier calipers, and the divisions with a slide 

 rule. The proportions given are mostly divisions either of the 

 standard length or of the head. The standard length is the distance 

 between the anterior extremity of the head and the base of the caudal, 

 that is, the end of the vertebral column as near as it may be deter- 

 mined without dissection. Proportions given merely as "in length" 

 mean in the standard length. Proportions given as "in head" apply 

 to the distance between the anterior extremity of the head and the 

 most distant part of the bony margin of the opercle. Any deviation 

 from the customary rule in making the measurements and in obtaining 

 the proportions, as set forth in the preceding sentences, is explained 

 in the descriptions. 



The proportions pertaining to the eye are based on its horizontal 

 diameter; the length of the snout on the distance between its anterior 

 tip (whether composed of its own tip or that of the upper jaw) to the 

 anterior rim of the orbit; the "interorbital" on the distance between 

 the margins of the bone or bones between the middle of the eyes; 

 the interorbital space on the distance between the upper margins of 

 the eyes; the maxillary on the distance between the median point 

 of the upper jaw to the posterior extremity of the maxillary bone; 

 the proportions pertaining to the caudal peduncle are based on its 

 least depth; and those of depth are based on the greatest depth of 

 the body. 



Some abbreviations have been adopted for the purpose of saving 

 space. The expression "Head 3.1 to 8.5; depth 2.8 to 3.2" signifies 



