272 t\ H. EDdEWORTH. 



galas, Acipenser) branchial bar, oi- to the shoulder-girdle, 

 formiug a coraco-maiidibularis (Scyllium, Ceratodus, Poly- 

 pterus ? species, described by Fiirbringer). 



The anterior attachment of the genio-hyoid and coraco- 

 mandibularis is to the front end of Meckel's cartilage except 

 in Anuran larvee, where it is to the inferior labial cartilage. 

 In Acanthias, where there is an inferior labial cartilage 

 (Gaupp), the coraco-maudibularis is not attached to this but 

 to Meckel's cartilage. In Callorrhynchus (Fiirbringer) there 

 is a coraco-prasmandibularis developed, attached anteriorly to 

 the inferior labial cartihige. 



Fiirbringer honiologised the genio-hyoideus with the 

 coraco-mandibularis of Selachii, and supposed that the 

 former was derived from the latter, by giving np its attach- 

 ment to the shoulder-girdle, and gaining a new one to (more 

 rostally lying) portions of the hyobranchial skeleton. Such 

 a deduction was a legitimate one from the evidence of adult 

 anatomy only, though the alternative was possible, and 

 the embryological history of the muscles shows that it is 

 this alternative which occurs; the condition in Teleostomi, 

 Elasmobranchs, and Ceratodus is a secondary one. 



The method of development of the hypobranchial spinal 

 muscles in Scyllium lends additional interest to, and receives 

 corroboration from, some anatomic;il facts described by Vetter 

 and Fiirbringer. The degree of backward extension of the 

 coraco-mandibularis towards the shoulder-girdle varies, even 

 amongst the Selachii. Thus in Heptanchus and Scyllium it 

 does not reach the coracoid, whereas in Lgemargus and 

 Prionodon it does. Further, the coraco-mandibularis is not 

 crossed by tendinous inscriptions, in this forming a marked 

 contrast to the coraco-hyoideus, alongside of which it lies. 

 The only possible exception to this among the forms depicted 

 by Fiirbringer is Cestrastiou, and this is probably an apparent 

 one only; it is possible that the tendinous inscription really 

 separates the coraco-hyoideus from the coraco-manibularis, 

 which only reaches the coracoid by its median edge. 

 Similarly, according to Fiirbringer, there are three tendinous 



