The Anatomy of Chlamydoselachus 



391 



The first [coracobranchialis muscle] has its origin in the connective tissue directly over 

 and attached to the coracohyoideus muscles. The origins of the second to the sixth coraco' 

 branchiales are in the strong connective tissue just dorsal to the coracoarcuales. The anterior 

 part of the origin of the seventh is continuous with the origin of the sixth while the posterior 

 part has its origin on the pectoral girdle, just lateral to the origin of the coracoarcuales. 



Until we know more of the relations of the sheet of connective tissue that affords 

 origin to the coracobranchiales of Heptanchus we cannot be sure that these muscles 

 have any real connection with the coracoarcuales. Comparison should be made directly 

 from dissections of the two forms. 



The muscle which AUis calls the pharyngo-clavicularis is described by him (1893, 

 p. 195) as follows: 



Immediately dorsoposterior to the surface of insertion of the coracobranchialis VI on 

 the sixth ceratobranchial, a broad muscle has its origin, and running ventromesially and 

 contracting rapidly has its insertion on the clavicle dorsolateral to the coracoarcualis muscle 

 of its side. This muscle would seem to be the homologue of the pharyngo-clavicularis of 

 Amia (AUis, 1897), and it is not described by Vetter as a separate muscle in any of the 

 selachians considered by him. 



The Eyeball Group. — In elasmobranchs and perhaps in vertebrates generally, 

 the muscles that move the eyeballs arise (Marshall, 1881; Van Wijhe, 1883; Neal, 1918) 



Vcrbindung dcs 



Kiemenbogen- 



coeloms mit dem 



CavLim pericardii 



Text-figure 65. 



Diagrams showing the origin of eye muscles, and the extensions of the primitive coelomic 



cavity into the gill-arches, in selachian embryos. In A, the cavities of the pharyngeal 



arches are shown communicating with the pericardial portion of the coelomic cavity; in B, 



which is a later stage, the connections of these cavities have been lost. 



I> 2, 3, 4, gill-clefts; S.B.C.l — 5, pharyngeal arch extensions of the coelomic cavity; ch.dors., chorda dorsalis; 



oc.m., anlagen of the oculomotor muscles; M. obUq. sufj. and M.rect.lat., anlagen of the superior oblique and lateral 



rectus muscles respectively; nes. audit., otic vesicle. 



After Corning, 1925, Figs. 222 and 223; based on Froriep's (1902) Figs. 4 and 5 (Torpedo ocdlatus). 



