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Bashford Dean hiemorial Volume 



figured as a complete and separate group. The coracoarcuales and coracobranchiales 

 muscles of one side of the head are shown in Text-figure 64 after Gregory, and the 

 first pair of coracobranchiales (cb.l) are shown in my Figure 8, plate III. Allis (1923, 

 pp. 192-195) gives a detailed description of each of the muscles under consideration. 



idhy cjdd'id' ad.arc i''P^- /^i" 



ad-arc ^ 



leir.lab.sup. 



„ , cb^A / care 



pmang.or lab.cart ^^^^^^ ' J^ ^^^s 



Text-figure 64. 

 Skull and visceral arches of Chlamydoselachus with the deep muscles of the branchiocranium. These 

 muscles fall into two main groups: extensors of the oral and branchial arches, running anteroposte- 



riorly; and flexors, running vertically. 

 ad.arc, musculi adductores arcuales 1-6. ad.d., musculi adductores dorsales 1-5; ad.mand., musculus adductor mandibulae; 

 care, musculus coracoarcualis; cb., musculi coracobranchiales 1-6; co.sc, coracoscapular arch; hyom., hyomandibular; id., 

 musculi interdorsales 1-5; id.hy., interarcualis between hyal and first branchial arch; lab.cart., labial cartilages; lev.lah.sup., 

 musculus levator labii supcrioris; lev.mx.sup., musculus levator maxillae superioris; pal.qu., palatoquadrate; pro.ang.or., 

 musculus protractor anguli oris; trpz., musculus trapezius. 

 After Gregory, 1933, Fig. 4. 



As one would expect from the similarity of their cartilaginous branchial frame- 

 works, there is a marked likeness between the hypobranchial musculatures of Chlamy^ 

 doselachus and Heptanchus. Only a few points call for special consideration here. 



There are, to be sure, only six pairs of coracobranchiales in Chlamydoselachus, as 

 compared with seven in Heptanchus, but this difference is correlated with the number 

 of gill arches. Of these muscles in Chlamydoselachus, Allis (1923) says: "The more 

 posterior coracobranchiales have no connection whatever with the musculi coraco- 

 arcuales, Chlamydoselachus differing markedly in this respect from Heptanchus (Vetter, 

 1874) and closely resembling Acanthias (Vetter, I.e.)." In Vetter's figure of Heptanchus 

 (his Fig. 9, pi. XV), the coracobranchiales of the region under consideration appear to 

 arise directly from the muscuH coracoarcuales, while one gets a somewhat different 

 impression from Davidson's figure reproduced as my Text-figure 63. Davidson (1918, 

 p. 162) describes the origin of the coracobranchiales muscles of Heptanchus as follows; 



