30 



SHOULDER-GIRDLE AND BREAST-BONE. 



clavicles meet in front of the inter-clavicles ; not so in Sturio and Coccosteus. The bones lettered 

 d' may either belong to the post-clavicular cincture, or they may answer, in their subcutaneous 

 portion, to the second pair of inter-clavicular bones soon to be described in the Lophobranchii. 

 The key-stone pieces b, e, are the exact counterparts of the first two " abdominal-line " plates of 

 the Lophobranchii, e. g. Hippocampus, Syngnatlms, Pliyllopteryx. Counterparts of these bones 

 are also familiarly known in the Clupeoids (see YarrelPs ' British Fishes/ 1836, vol. ii, p. 107 ; 

 where a figure of one of these, from the Pilchard, is given). As it is necessary to call in the 

 Sturgeon and Sea-Horse to explain the Coccosteus, it may, perhaps, be well to leave its classifi- 

 cation in a provisional condition for the present. 



B. LOPHOBRANCHII. 



The Siluroids once passed, a great change is seen even in those Fishes that still retain the 

 ganoid armour ; for the inner portion of the dermal system of bones is now differentiated from 

 the outer, and is correlated more perfectly to the contiguous parts of the endo-skeleton. 



SHOULDER-PLATES OF HIPPOCAMPOIDS. 



SYNGNATHUS Acus, LINN. 

 A and C. Right side, inner view. B. Lower view of right and left side. 



FIG. 3B. 

 FlG - 3 A. , ,. . 



/n/r w j- \ (Magn. 7 diam.) 



(Magn. 7 diam.) 



i. 1. 1. 



FIG. 3 C. 



(Magn. 10J diam.) 



4.4. 



a. 1. 1. 



a. i. cl. p. i. cl. al. 2. 



The Hippocampoids may be described first, and the great Pipe-Fish (Syngnatlms acus) 

 may be taken as the type. Here the large, leaf-like, ganoid scales can be entirely dissected 

 away from the clavicular cincture : this latter system of bones will be found to be strong, although 



al. -2. 



