THE SHOULDER-GIRDLE IN FISHES. 39 



Fain. " GASTEROSTIDJE." 



Example. Gasterosteus leiurus, Cuv. and Val. 



I have long been familiar with the skeleton of such " Mailed-cheeked" Fishes as the Triglce 

 and theCottoids; but my attention has lately been directed to the Sticklebacks (Gasterostet) . 

 Professor Huxley sometime since ('Proc. Royal Soc.,' Nov. 18, 1858; and 'Microscop. Journ./ 

 Oct., 1858, vol. vii, pp. 83 46; and Jan. 7, 1859, pi. iii) worked out some most valuable 

 results from the commonest kind, viz, G. leiurus. His researches have had regard to 

 the development of the skull and of the tail; this latter part of the Fish is shown to be truly 

 " heteroceral ; " and in the figure given of the face of the adult Fish ('Croon. Lect.,' p. 27, 

 fig. 7) I long ago detected an instance of connation, very remarkable indeed if this be a typical 

 Acanthopterous Fish. I refer to the palatine bar (pa.), which has no separate "pterygoid," but 

 at once articulates with the " quadratum " (Qu.}. My present remarks are upon the Shoulder- 

 bones of the adult Fish, and they satisfy me that this is not one of the ordinary Acanthopteri ; 

 I shall therefore consider them as belonging to a very special Family, but leave the Order 

 in which they should be placed to some other Ichthyotomist. 



Altogether, the morphology of the dermal skeleton of Gasterosteus carries us back again to 

 the same ichthyic level as the Siluroids ; the Lophobranchii and the Plectognathi come much 

 nearer to the typical Fishes, and thus diverge much further from the true Ganoids than these 

 familiar little denizens of our fresh-water pools and canals. The Ganoidei are hemmed-in on 

 all sides by Genera and Families of Fishes that are aberrant from the higher types ; none of 

 these press much nearer to those ancient Fishes than the Sticklebacks. There are scarcely any 

 morphological characters that express generalization in the Fish-Class better than connation of 

 dermal plates with ossified subcutaneous tracts, and coalescence of these bony parts with true 

 endo-skeletal elements ; both these characters are well exemplified in the Gasterostei. 



The " post-temporal " (fig. 5 A, p. t.) is a fan-shaped ganoid plate, strongly articulated 

 to the outer angle of the occiput ; it has a strong subcutaneous peg at its antero-inferior angle. 

 The " super-clavicle " is not distinct from the clavicle, a character seen in Clarias ; in one side of 

 CallicJithys ; and in Syngnathus. 



The clavicle (cl.) is continuous with the supra-clavicle and is very large ; it is connate with 

 a quadrant-shaped ganoid plate, from the hinder part of which there projects a sharp spur, and 

 along the front of which the supra-clavicular bar runs upwards and forwards. The body of 

 the bone proceeds downwards and forwards from the base of the upper spur, and from the sharp 

 and serrated lower edge of the ganoid portion ; it is a thick rod, with a long, sinuous, concave 

 wing in front, and a shorter convex wing externally. The clavicle reaches nearly to its fellow 

 below, and articulates with the anterior angle of the inter-clavicle (i. cl.). 



Above the ganoid part of the clavicle there is a small oval ganoid ossicle (fig. 5 A, 1. 1. 2) ; 

 this belongs to the second thoracic cincture ; it answers to the second lateral-line bone, and is 

 the serial homologue of the " post-temporal." The next ganoid plate (fig. 5 A) is more like the 

 post-temporal, but is not half its size ; it is perforated by a mucous duct. The next is oblong, 

 with triangular ends, and much larger; it answers, in its own cincture, to the post-temporal and 



