129 
EXPLORATIONS IN WESTERN CANADA, ETC. 
LOCAL VARIATIONS.* 
Since all structures clitFering from tlie aveiage are usually confined to a definite 
horizon or more or less restricted region, all such differences may be considered local 
variations. The larger zoogeographical regions or provinces are in this extended 
sense localities, and the orders, families, or species are the local variations peculiar to 
the region or province. A somewhat more restricted definition would include such 
phenomena as are noticed in the peculiar modifications of the fins of Pacific slope 
fresh water fish described in the previous cliapter. Some (.hjprinida of the Colorado 
basin, for instance, have the anterior dorsal rays stiong and spinous, while all the 
Atlantic slope species have them weak and rudimentary. Anotlier instance is the 
increased number of rays in the fins of Pacific slope fishes. Still another instance is 
offered by the Ferco 2 )sidce. Columbia has strong spines in both the dorsal and anal 
fins, while Percopsis, the Atlantic slope genus, has none. 
For the present purpose I want to restrict the meaning still further. In studying 
the South American catfishes, I found that all the Amazonian species of the genus 
lihamdia have G dorsal rays, while several of the southern forms have more. One 
peculiar to the La Plata has G-9; another from the San Francisco has 10 rays. More 
remarkable still is the case of Pseudopimelodus zuugaro. All the specimens taken in 
the Amazon have G dorsal rays, while of a smaller number taken further south several 
have 7 dorsal rays. 
It is to variations like the last, i. e., variations within the species or closely related 
species found in different localities within a restricted region, that I want to confine 
my present remarks. Variations within species are a matter of lines and curves, 
minute measurements, and shades of color: all matters difficult to keep in mind, still 
more so to represent to others. All naturalists are aware of the existence of slight 
differences peculiar to different localities, but such variations are usually Init vaguely 
eonceived by the observer, and still more vaguely by any one to whom the observer 
may attempt to explain them. 
The past summer I collected a large series of specimens oi‘ Leaciseus and Kichat'd- 
sonius. These were taken in a number of different localities and in two separate 
river systems, the Columbia and the Fraser. The localities extend from tide water 
to an elevation of 1,900 feet on the Fraser, and from 300 to 4,700 feet on the Columbia 
system. 1 have also examined a number of specimens collected by Dr. Jordan in 
Utah. There were in all 29G specimens which 1 was personally able to examine. In 
these specimens the local variations are so well marked that a graphic method of 
demonstrating the variations is possible. 
Before attempting to exjjlain the charts which illustrate this matter, it is neces- 
sary to state that there have been known from the two river systems two groups or 
genera of Cyprinidw having elongate anal tins. These w'ere Rieka rd.sou ins (balteatus 
and lateralis) and a section of Leucisens (ntontanus, kydrophlox, and yilli). There are, 
first, variations which do away witli the genus Richardsonins, as distinct from Leucis- 
ens ; second, a number of variations which, while very striking, need not be taken 
into consideration, because the variations in a single character are sufficient for our 
purposes. We shall limit the observation to the variation in the number of anal rays. 
* Read at the December meeting of the Indiana Academy of Sciences, 18‘J2. 
F. C. B. 1891—9 
