Fig. 439.—Diodon geometricus. (After Goode.)
Only two genera appear capable of clear definition: Diodon and Lyosphaera; species about 15. Numerous species have been described from the Upper Eocene and later formations.
"Porcupine Fishes" are confined to tropical seas, and have attracted attention from the earliest times, being frequently preserved as "curiosities." Their flesh is regarded as poisonous.
Fam. 3. Molidae.—Beak without median suture. Interoperculum rod-like, attached posteriorly to the rod-like anterior limb of the suboperculum. Gills 4. Anterior praecaudal vertebrae with divergent bifid neural spines and neural canal not roofed in. Body non-inflatable, truncate posteriorly, without caudal peduncle; caudal fin absent, the dorsal and anal fins confluent. Skin rough or tessellated. Vertebrae 17 in Orthagoriscus.
The very young are armed with spines.
Fig. 440.—Orthagoriscus mola. (After Goode.) × 1⁄20.
The "Sun-Fish" are extraordinary creatures found in the open sea or descending to great depths, and of wide distribution. The number of species is still very uncertain, but two generic forms, Orthagoriscus or Mola and Ranzania, are easily distinguished. Examples of both occur now and then on our coasts. Orthagoriscus mola grows to upwards of 8 feet and to a weight of 1800 pounds. It has been observed to swim slowly about, near the surface, the high dorsal above the water. Its food is said to consist chiefly of jelly-fish and larval fishes; its mode of reproduction and places of breeding are still unknown.