ANATOMY OF CACOPUS SYSTOMA. 



54r 



by the cartilaginous portion of the mentomeckelian (text-fig. 16 A). 

 The inner divisions of the two geniohyoideus muscles are still 

 further remarkable, for, in the region of the basi-hyal, they fuse * 

 to form an extensive median sheet of muscle with two posterior 

 oifshoots, each of which, spreading on a posterior cornu, entirely 

 conceals the hyoglossus muscle in the usual position of the toad 



Text-figure 15. 



M.M. 



S.M. 



,3. 



A view of certain superficial muscles of the hj'oid and deep-lying ones of the floor 

 of the mouth. The lower jaw (L.J.) has been divaricated ; the suh-maxillaris 

 and the " swb-Jiyoidetis " have been removed ; a right half of the xiphisternum 

 has been cut away in order to expose at their origins the inner portion of the 

 sternohyoideus (ST. I.) and the " abdominis-siernalis " (A.S.). R.A., coutinua 

 tion of the " inner division of the rectus-ahdominis " as the " outer portion of 

 the sternohyoideus " ST. ; 1.3 and 1.4, third and fourth inscriptio-tendina of 

 R.A.' respectively; F.M., certain muscle-fibres between the lower jaw and the 

 cartilaginous part of a mentomeckelian. For other letters consult the key-list 

 of abbreviations. 



during dissection. The insertion of the former, in consequence 

 of its extensiveness, is extraordinary ; for it consists of a peri- 

 meter of the inner lateral edges of the two posterior cornua and 

 the hind border of the basi-hyal enclosed between these two 

 cornua, thus forming a parabolic curve (text-fig. 16 B, G."). 

 The single " outer portion of the sternohyoideus " (or the 



* A condition similar to this has been observed by Beddard (1) in Sreviceps. 



Proc. Zool. Soc— 1922, No. XXXVIII. 38 



