59 



Pig. 3. 



Figs. 1 and 2 represent the lower portions of the Visceral arches in Hexanchus as 

 seen from above. Fig. 3 represents the Cartilages lying in front of Hyoid arch in 

 Lasmargus. 



A Cartilages between mandibular and hyoid arches ; Bhr. Basibranchials ; Bh. Basi- 

 hyal; BH Upper anterior edge of Basihyal ; Bm. Basimandibular ; Br. 1 — 6 Branchial 

 arches; Cb. 1 — 6 Ceratobranchials ; Ch. Ceratohyal ; Ky. Hyoid arch; Hb. 2 — 5 Hypo- 

 branchials ; M. Mandibular arch. 



Having found these cartilages in Hexanchus I next turned my 

 attention to L se m a r g u s , to see if any cartilages could be found in a 

 similar position. I have at present six heads of this shark by me, 

 and although I have looked carefully it is only in one case that I 

 find traces of these cartilages. In this specimen I find eight small 

 nodules (Fig. 3 J.), four on each side of the middle line, lying in the 

 connective tissue on the anterior face of the basihyal, and some 

 distance below its upper border {ßlfi). The figure represents the 

 natural size and arrangement of the cartilages and their relative 

 position to the upper edge of the basihyal in a shark about eight 

 feet long. 



Four other cartilages ranged in front of the hyoid arch I have 

 already drawn attention to in my paper onLtemargus, and as they 

 lie much on the same plane as those I have first noticed I may again 

 refer to them. One pair ot these bear the same relation to the lower 

 extremities of the ceratohyals as the first pair of hypobranchials do 

 to the ceratobranchials of the first branchial arch, and I have regard- 

 ed them as hypohyal elements. These cartilages are in some cases 

 absent and there may be two cartilages on one side. 



Besides these supposed hypohyal elements, there is at the lower 

 and anterior part of the hyomandibular, on each side, a rounded 

 nodule of cartilage lying in the ligament connecting that cartilage 



