72 THE CYPRINODONTS. 
the upper side of the orbit for the protection of the eye. In the bases of 
the pectorals the carpal elements are nearly obsolete, those remaining are 
very small; the clavicula and other coraco-scapular bones are thin and 
broad, but strong and firmly attached. Posteriorly the two processes of 
the hindmost vertebra form a fan of medium size, in which the line of 
junction is distinct. All of the species in the genus, as known at present, 
have a convex posterior margin to the caudal fin. The halves of the 
pelvis are widely separated. More than half of the length is occupied 
by the body cavity. 
In its earlier stages the young Anableps bears some resemblance to Rivu- 
lus. At this time the eye is not traversed by the band of the conjunctiva, and 
the pupil is not divided by projecting lobes of the iris. The eyes are not 
very prominent above the crown; the latter is arched. The dark band 
across the cornea, the bony shield above the orbit, and the lobes in the pupil, 
dividing it into an upper section and a lower, are of later appearance. A 
peculiar feature of the embryo is the abdominal pouch, or bag, containing 
the intestines, below the permanent ventral walls. This pouch gives the em- 
bryo of Anableps an outline similar to that of Gambusia (see Plate VI. Fig. 1). 
It extends from the shoulder girdle to the vent, separates the ventrals perma- 
nently, and communicates with the body cavity by a slit that extends from 
the vent forward nearly to the coraco-scapular arch. Its surface bears nu- 
merous lines of more or less confluent papillae, converging from the body 
downward to a point near the middle of the lower side. These papillex 
mark the courses of the blood vessels from which they rise and into which 
they pour the food supply drawn from the portion of the egg remaining with 
the embryo inside the egg-envelopes. Near the heart, near the vent, and 
around the lower point of convergence the papille are larger, in cases unit- 
ing and forming continuous ridges. Possibly in addition to their absorbent 
function they also serve a purpose in oxygenating the blood. They persist, 
after the egg envelopes are ruptured, for a time, until the young in the 
ovarian chamber have reached a length of about two inches; then the sac 
becomes thin and with the papillee is itself absorbed. The yelk is exhausted 
by the time the embryo has attained a length of half an inch ; the continued 
growth of body and sac is, within the ege coverings, nourished from the 
included albumen, or later, from the liquids by which the sac is surrounded 
in the cavity of the ovary. After the fish has nearly completed its pre- 
natal development the intestines gradually withdraw from the bag into the 
