CATOSTEOMI 627 



further support from the recent investigations of Swinnerton, 1 

 who has proposed to unite the two groups under the new 

 name of Thoracostei. The name Phthinobranchii has also 

 been suggested by 0. 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, 2 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 3 that the Lamprididae are 

 related to the Hemibranchii, although sufficiently distinct to 

 warrant the establishment of a division, named Selenichthyes. 4 



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. 



1. Pelvic 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. 

 - 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 Charac- 

 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. 



