XXII CATOSTEOMI 627 
further support from the recent investigations of Swinnerton,! 
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,’ 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’ that the Lamprididae are 
related to the Hemibranchi, although sufficiently distinct. to 
warrant the establishment of a division, named Selenichthyes.* 
SYNOPSIS OF THE FAMILIES. 
I. Praeopereulum 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. 
IL. Praeopereulum and symplectic distinct, latter much _ elongate ; 
branchial apparatus more or less reduced; gills pectinate ; post-temporal 
simple, immovable ; mouth terminal (HEMIBRANCHIT). 
A. Mouth toothed. 
1. Pelvie bones usually connected with scapular arch ; spinous 
dorsal represented by isolated spines. 
Snout conical or but slightly tubiform; ventral fins with 1 spine and 1 or 
2 soft rays; ribs slender, free ; anterior vertebrae not enlarged 
2. Gastrosteidae. 
1 Quart. Journ. Micr. Sci. xiv. 1902, p. 503. 
2 Ann. Sci. Nat. (8), xiv. 1902, p. 197. 
3 Ann. Mag. Nat. Hist. (7) x. 1902, p. 147. 
4 E. C. Starks, in an important paper on ‘‘The Shoulder Girdle and Charae- 
teristic Osteology of the Hemibranchiate Fishes” (Proc. U.S. Nat. Mus. xxv. 1902, 
p- 619), has shown that the so-called infraclavicle of Sticklebacks and allies does not 
exist as a distinct element. The definition of the Catosteomi, as I had originally 
drawn it up, has accordingly had to be modified. 
