44 Descriptions of Preparations. 



drosis between the hyomandibular and the symplectic. The rect- 

 angular praeoperculum by opposing itself to the posterior and outer 

 edges of the hyomandibular^ symplectic, and quadrate, at once 

 clamps them together into a coherent suspensorial pedicle, and 

 brings the entire apparatus into as direct a functional relation with 

 the true opercular bones posteriorly as that into which it is brought 

 anteriorly with the upper jaw through the meta- ento- and ecto- 

 pterygoids. 



Riblike ossifications of the intermuscular aponeuroses are attached 

 to the neural arches of the two first trunk vertebrae and to the 

 true ribs of the succeeding twelve. The majority of these latter 

 structures are appended to the extremities of the parapophyses, 

 which again in the caudal region bend down and fuse at their 

 apices, to form a haemal canal. 



The pectoral fin with the four brachials, scapula, and coracoid, 

 is supported on an arch consisting of three parostotic bones. The 

 uppermost of these, a forked bone, suspends the arch to the squa- 

 mosal and epiotic bones by its two branches ; it has been called the 

 ' supra-scapula,^ but is not homologous with the structure properly 

 so named in placoids and sturgeons, being in reality the first 

 ' lateral line^ scale bone, and perforated, as the insertion of a bristle 

 shows, for one of the muco-nervous tubes of that system. It over- 

 laps the clavicle from the outside, and this latter bone, after giving 

 support to the true scapula and coracoid, comes into relation with 

 the apex of its fellow of the opposite side, in the middle line, with 

 the bones supporting the ventral fins, posteriorly, and with the 

 urohyal in front. The scapula has a sub-circular fenestra ; it gives 

 support directly to some of the upper rays of the pectoral fin, and 

 mediately by the two upper and smaller of the four brachials to a 

 larger number of these rays ; the lowest of the four brachials is 

 carried by the coracoid ; and a fourth finds a glenoid facet for itself 

 on the lower edge of the scapula, the upper edge of ih.Q coracoid, 

 and the line of suture between them. The clavicle overlaps a 

 postclavicular bar consisting of two bones, one squamiform and 

 placed superficially, the other styliform and placed beneath the 

 integuments in the fresh state. 



A number of muco-dermal bones lie on the exterior of the 

 cranium and are connected with the system of the lateral line. 



Six such, of which the most anteriorly-placed is the largest, form 



