Royal Microscopical Society. 257 



could not have guessed in the least the original state of these parts 

 in the Sturgeon. Let the reader imagine a second /-shaped bar 

 behind the mouth like the first and of the same size ; this bar, round 

 at first, flattens out, and then divides into two similar rods, the 

 hinder the slenderer of the two. These get a distance from each 

 other, and apply themselves to the ear-capsule, as if they were 

 primary rods. The foremost has a small nodule segmented off from 

 its lower end, and a larger piece above this becomes separate. Then 

 the hinder piece gradually lets itself down near the lower end of the 

 bar in front, gets the lowest nodule attached to its extremity, fastens 

 itself to the middle segment near its top, and has a nodule of car- 

 tilage formed in the suspensory ligament. 



Then the upper segment of the anterior bar, the "hyoman- 

 dibular " or " incus," flattens out, and projects backwards to form a 

 shoulder, on which the great " opercular " bony plate is situated ; 

 and above this part a sheathing shaft-bone is formed, below the 

 rounded articular head. This piece is attached by a fibrous band 

 to the segment below, which is like a phalangeal bone, with its 

 shaft; this is the " symplectic/' which in Osseous Fishes is only 

 separated from the " hyomandibular " by an unossified tract of 

 cartilage. The oblique inferior end of this free phalangiform 

 " symplectic " is bound by ligament to the quadrate region and to 

 the angle of the jaw. The little secondary block of cartilage which 

 is formed in the ligament which binds the two hinder to the two 

 front cartilages of the hyoid arch, occurs as a larger rod in Osseous 

 Fishes, and is constant, I believe, in Mammals. In Man it is known 

 to anatomists as a little rod running with the tendon of the stape- 

 dius muscle towards the " stylo-hyal," and is attached to the 

 neck of the " stapes." It is the " inter-hyal." Below this binding- 

 joint is the true " stylo-hyal " ; it is phalangiform, and has enlarged 

 ends like the rickety phalanges of a weak, young, captive Mammal ; 

 its shaft-bone surrounds it. The lowest segment is the counterpart 

 of the " lesser horn," " cornu minor " of the human tongue-bone. 

 This " cerato-hyal " is attached to the "stylo-hyal" by ligament 

 (Fig. 4, st. h., c. h.) and by ligamentous fibres, vtiihout&joint-eavtiy 

 are nearly all the parts attached in the Sturgeon's face, the exceptions 

 being the " glenoid " articulation, or that of the mandible with the 

 "quadrate," and the hingeing of the hyomandibular on the ear- 

 capsule. It may sound strange in the ears of some that the 

 elements that go to make up the mouth of such a creature as the 

 Sturgeon should be boldly named by the very terms used in 

 the description of the human palate, mouth, and throat ; but it 

 must be remembered that a knowledge of the true representative 

 elements, in forms so wide apart, has not come of itself to anatomists. 

 There has been long and anxious work, by many skilled workers, to 

 bring this about. 



