The Mormyridæ.—There are two families of Scyphophori. The Mormyridæ have the ordinary fins and tail of fishes and the Gymnarchidæ are eel-like, with ventrals, anal and caudal wanting. Gymnarchus miloticus of the Nile reaches a length of six feet, and it is remarkable as retaining the cellular structure of the air-bladder as seen in the garpike and bowfin. It doubtless serves as an imperfect lung.
The best-known genus of Scyphophori is Mormyrus. Species of this genus found in the Nile were worshiped as sacred by the ancient Egyptians and pictures of Mormyrus are often seen among the emblematic inscriptions. The Egyptians did not eat the Mormyrus because with two other fishes it was accused of having devoured a limb from the body of Osiris, so that Isis was unable to recover it when she gathered the scattered remains of her husband.
In Mormyrus the bones of the head are covered by skin, the snout is more or less elongated, and the tail is generally short and insignificant. One of the most characteristically eccentric species is Gnathonemus curvirostris, lately discovered by Dr. Boulenger from the Congo. Fossil Mormyridæ are unknown.
Fig. 149.—Gnathonemus curvirostris Boulenger. Family Mormyridæ. Congo River. (After Boulenger.)
The Haplomi.—In the groups called Iniomi and Lyopomi, the mesocoracoid arch is imperfect or wanting, a condition which in some cases may be due to the degeneration produced by deep-sea life. In the eels a similar condition obtains. In the group called Haplomi (ἁπλοός, simple; ὤμος, shoulder), as in all the groups of fishes yet to be discussed, this arch is wholly wanting at all stages of development. In common with the Isospondyli and with soft-rayed fishes in general the air-bladder has a persistent air-duct, all the fins are without true spines, the ventral fins are abdominal, and the scales are cycloid. The group is a transitional one, lying almost equidistant between the Isospondyli and the Acanthopterygii. Gill unites it with the latter and Woodward with the former. We may regard it for the present as a distinct order, although no character of high importance separates it from either. Hay unites the Haplomi with the Synentognathi to form the order of Mesichthyes, or transitional fishes, but the affinities of either with other groups are quite as well marked as their relation to each other. Boulenger unites the Iniomi with the Haplomi, an arrangement which apparently has merit, for the most primitive and non-degenerate Iniomi, as Aulopus and Synodus, lack both mesocoracoid and orbitosphenoid. These bones are characteristic of the Isospondyli, but are wanting in Haplomi.
There is no adipose dorsal in the typical Haplomi, the dorsal is inserted far back, and the head is generally scaly. Most but not all of the species are of small size, living in fresh or brackish water, and they are found in almost all warm regions, though scantily represented in California, Japan, and Polynesia. The four families of typical Haplomi differ considerably from one another and are easily distinguished, although obviously related. Several other families are provisionally added to this group on account of agreement in technical characters, but their actual relationships are uncertain.
The Pikes.—The Esocidæ have the body long and slender and the mouth large, its bones armed with very strong, sharp teeth of different sizes, some of them being movable. The upper jaw is not projectile, and its margin, as in the Salmonidæ, is formed by the maxillary. The scales are small, and the dorsal fin far back and opposite the anal, and the stomach is without pyloric cæca. There is but a single genus, Esox (Lucius of Rafinesque), with about five or six living species. Four of these are North American, the other one being found in Europe, Asia, and North America.
All the pikes are greedy and voracious fishes, very destructive to other species which may happen to be their neighbors; "mere machines for the assimilation of other organisms." Thoreau describes the pike as "the swiftest, wariest, and most ravenous of fishes, which Josselyn calls the river-wolf. It is a solemn, stately, ruminant fish, lurking under the shadow of a lily-pad at noon, with still, circumspect, voracious eye; motionless as a jewel set in water, or moving slowly along to take up its position; darting from time to time at such unlucky fish or frog or insect as comes within its range, and swallowing it at one gulp. Sometimes a striped snake, bound for greener meadows across the stream, ends its undulatory progress in the same receptacle."
