Fig. 382.—Fierasfer acus, penetrating into Holothurians, ⅖ nat. size. (After Emery.)
Sub-Order 7. Catosteomi.
Air-bladder, if present, without open duct. Parietal bones, if present, separated by the supraoccipital. Pectoral arch suspended from the skull; no mesocoracoid arch; coracoid usually very large. Ventral fins, if present, abdominal, or pelvis attached to the coracoid bones.
The mouth is small and bordered by the praemaxillaries or by the praemaxillaries and a small portion of the maxillaries. The air-bladder is present, except in the Solenostomidae and Pegasidae.
Following the suggestions of Kner and Steindachner and Cope to their logical conclusion, A. S. Woodward, in his valuable catalogue of the Fossil Fishes in the British Museum, has united the Lophobranchs of Cuvier with the Hemibranchs of Cope, a course which seems fully justified, and has received further support from the recent investigations of Swinnerton,[[698]] who has proposed to unite the two groups under the new name of Thoracostei. The name Phthinobranchii has also been suggested by O. P. Hay for the same association. The structure of the Lophobranchs (Solenostomidae and Syngnathidae) shows that these fishes are only extremely specialised forms of the group of which the Sticklebacks are the well-known type, and the character of the "tufted" gills alone is surely not of sufficiently great importance to warrant the retention of the Lophobranchii as a division equivalent to the sub-orders adopted in the present classification. Besides, as recently pointed out by A. Huot,[[699]] there is no fundamental difference, but only one of degree, between the so-called tufted gill and the normal type; each "tuft" corresponds to one branchial lamella, and at a certain stage of development the disposition of the branchial lamella is the same in a Syngnathus and in an ordinary Teleostean. I have recently attempted to show[[700]] that the Lamprididae are related to the Hemibranchii, although sufficiently distinct to warrant the establishment of a division, named Selenichthyes.[[701]]
SYNOPSIS OF THE FAMILIES.
I. Praeoperculum and symplectic distinct; branchial apparatus fully developed; gills pectinated; mouth terminal, toothless; post-temporal forked, free; pelvic bones connected with scapular arch; ventral fins with 15 to 17 rays; ribs long, sessile; fins without spines (Selenichthyes) .......... 1. Lamprididae.
II. Praeoperculum and symplectic distinct, latter much elongate; branchial apparatus more or less reduced; gills pectinate; post-temporal simple, immovable; mouth terminal (Hemibranchii).
A. Mouth toothed.