BY WILLIAM A. IIASWELL, M.A., B.SC. 95 



palatoquadrate. The hyoid is a stout, gently curved, cartilage more 

 than half as long again as the hyo-inaudibular. The rays are 

 connected with the hyo-mandibular only near the skull, and with 

 the hyoid for a short space some distance from the proximal end ; 

 the two sets curve round and meet, leaving a wide opening opposite 

 the articulation between the two cartilages ; they coalesce and sub- 

 divide in a highly complex manner. The spiracular cartilage is a 

 delicate lamella of oblong shape with the two inner angles and the 

 antero-external produced into short processes. 



The body of the hyoid is rather narrower than the branchial 

 copula and strongly arched forwards. Externally it presents two 

 cornua an anterior short and stout for articulation with the hyoid 

 and a posterior, rather longer for the copulare of the first branchial 

 arch. 



The ventral mesials of the first four branchial arches are longer 

 but narrower than the dorsals ; they both have deep excavations 

 for the adductor muscles, those of the dorsal cartilages being the 

 larger, and being perforated. The first arch bears ten rays, the 

 second likewise ten, the third eight, the fourth six ; a number of 

 the rays have hooked extremities. On the posterior border of each 

 ventral mesial cartilage, in continuation of the row of rays, is a 

 lamelliform process, very prominent in the first arch, becoming 

 very low in the fourth. A. slender cartilage represents the dorsal 

 end of an external branchial arch, and in the second, third, and 

 fourth arches, but not in the first, an irregular flattened cartilage 

 represents the ventral portion ; the first of these ventral cartilages 

 of the external branchial arches is not connected with the internal 

 arch ; the others articulate with the ventral mesials. The dorsal 

 portion of the fifth arch coalesces as usual with that of the 

 fourth. The dorsal mesial of the fifth is deeply excavated for the 

 muscle ; the ventral slightly. The latter is much thicker than 

 these of the preceding arches ; it presents two conical processes ; 

 the one on its inner, the other on its outer surface, the latter 

 nearly corresponding in position to the rays of the preceding 

 arches. 



