MORPHOLOGY OP CPANIAL MUSCLES IN SOME VERTEBRATES. 269 



and comco-hyoid/ The posterior end of the geuio-liyoid grows 

 backwards (Text-figs. -28, 29, 30], and becomes attached, in 

 Acipenser to the third hypobranchial, and in Amia by two 

 tendons, to the second and third hypobranchials and to a 

 median aponeurosis between the two coraco-hyoidei (Y-shaped 

 tendon of Allis). 



In Polypterus,? species, PoUard described the hypobranchial 

 spinal muscles as consisting of a branchio-mandibularis s. 

 genio-liyoidens extending from the symphysis of the lower 

 jaw to the first basi-brancliial, and of a coraco-byoideus which 

 had an additional tendon attached to the first cerato-brauchial. 

 Fiirbringer described the muscles as consisting of a coraco- 

 mandibularis extending from the symphysis to the shoulder- 

 girdle, and of a coraco-hyoideus. 



In Polyp terns Senegal us (Text-figs. 35, 06, 37), the 

 muscles consist of a genio-hyoideus and a coraco-hyoideus ; 

 the former extends from the symphysis backwards to the level 

 of the third branchial bar, where it ends by being attached to 

 the third cerato-brancbial and by a tendon which passes down- 

 wards and is attached to a little median ossicle lying between 

 the two coraco-hyoidei. The coraco-hyoideus extends from 

 the cerato-hyal backwards to the shoulder-girdle, and has no 

 tendon passing to the first cerato-branchial. 



G-reil stated that the " liypobranchial musculature " of 

 Ceratodus was developed from ventral downgrowths of the 

 third and fourth myotomes. He apparently included the 

 coraco-branchiales as well as the coraco-mandibularis and 

 coraco-hyoideus under this head, as the first-named were not 

 described as developing in the branchial region. It has been 

 stated above (p. 234) that the coraco-branchiales are developed 

 from the lower ends of the branchial myotomes. The hypo- 

 branchial spinal muscle Anlage spreads forwards (Text-hg. 39) 

 reaching the anterior extremity of Meckel's cartilage in 

 stage 43. The portion in front of the hyoid bar separates 

 ' Main portion of coraco-arcualis anterior (Vetter) in Acipenser ; 

 byopectoralis (MeMurrich). sterno-liyoideus (Allis) in Amia ; the term 

 used above is that of Fiirljrin''-er. 



