THE CYPRINODONTS. 9 
but reliance is not to be placed entirely on them. The same may be said of 
the anal fin, or other features, when taken alone. By means of the anal the 
family might readily be subdivided into three groups: a first, in which the 
anal is not modified on the male, a second, in which it forms a clasper with- 
out an urogenital tube, and a third, in which a tube passes to the extremity 
of the fin; but in the first we should have Haplochilinw with conical teeth 
and Cyprinodontinw with compressed tricuspidate, and in the second Gam- 
busiinw, with conical, and Peeciliine with compressed teeth, while in the 
third would be placed the conical toothed Anablepinew with the compressed 
tricuspidate toothed Jenynsiinx, both of which are still more widely separated 
by the eyes and the ventral fins. To depend on the teeth alone would bring 
together the Cyprinodontinew, Jenynsiine, and some Peeciliinw, by the com- 
pressed and fixed dentition; by the conical shapes, Haplochilinw, Gam- 
busiine, and Anablepinew would be included; and by the oar-shaped and 
movable, only a part of the Pceciliinw would be placed. The unnatural 
nature of such arrangements is sufficiently evident. 
Five or six branchiostegal rays are most common; in a few types the 
number is smaller. 
With the variety in the food, the gill rakers vary in the different genera 
from short and tubercular to elongate. 
The greatest departure from the average vertebra is seen in Anableps 
where each side of each segment of the column over the body chamber has 
an elongate triangular process, grooved on the upper side, to the end of 
which the rib is attached. Great breadth of back with shortness and greater 
strength of rib is secured in this genus by means of these processes. At the 
base of the tail behind the terminal vertebra the processes forming the sup- 
port of the central portion of the caudal are broad and fan-like posteriorly 
throughout the family ; in some instances the hindmost pair anchylose, and 
form a single broad expanse, in which the original lines of separation are 
‘hardly visible. In number the vertebrae vary considerably. Anableps has 
more than fifty; certain species of Cyprinodon have hardly half as many. 
A peculiar modification of several of the vertebra is to be noticed on males 
of some species, in which the anal fin is modified and carried forward; an 
inferior process from the centra of two or more of the vertebra over the 
hinder portion of the body cavity is sent down to furnish support for the 
base of the transformed fin, Plate VIII. In Peecilia there are two of these 
stays; in Gambusia there are two in one species, and three, with more or 
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