724 MR FRANK J. COLE 



the former passes internal to the superior lateral cartilage and the latter external to it. 

 In the meantime, therefore, and in the absence of any information at first hand as to 

 its innervation, I follow Furbringer in separating this muscle from the constrictor 

 pharyngis. 



The cranio-hyoideus is a small but an interesting and curious muscle. In one 

 specimen dissected it arose as follows : — (a) a few fibres from the posterior edge of the 

 bridge of soft cartilage connecting the auditory capsule with the upper extremity of 

 the hyoid arch ; (b) most of the fibres from the ventral and posterior surfaces of the 

 posterior end of the auditory capsule ; (c) a few fibres from the external border of the 

 parachordal immediately behind the auditory capsule. Allis # states that in 

 Bdellostoma this muscle arises from the notochordal sheath immediately posterior to 

 the auditory capsule. In my sections it arose exclusively from the auditory capsule 

 on the right side, and on the left side partly from the capsule and partly from the 

 fascia covering the soft cartilage of the postero-lateral extremity of the parachordal. 



Just below its origin the cranio-hyoideus narrows down to pass under the root of 

 the superior lateral cartilage, and emerges below it between the hyoid and first 

 branchial arches. It at once fans out so as to occupy a part of the space between the 

 above two arches, and now proceeds in a vertical curve downwards and slightly back- 

 wards. It crosses externally, and obscures, the flat posterior process of the hyoid 

 arch, the origin of the most posterior fibres of the copulo-quadratus profundus, the 

 insertion of the hyo-copulo-palatinus into the first branchial arch, and the inferior 

 lateral cartilage, but passes internal to the copulo-quadratus superficialis. Hence this 

 muscle passes through the fourth fenestra of the skull. 



Below the flat posterior process of the hyoid arch the fibres of the cranio-hyoideus 

 converge again, and in a 35 cm. Hag were inserted into the external surface of the 

 most ventral 2 mm. of the first branchial arch (i.e. just where this fuses with the basal 

 plate), external to the insertion of the large posterior bundle of the hyo-copulo-palatinus 

 and the origin of the hyo-copulo-glossus. In one series of sections it was inserted into 

 the external surface of the first branchial arch somewhat dorsal to its fusion with the 

 basal plate, but in another series the insertion was as above described. 



On the right side of my large series of sections the cranio-hyoideus was vestigial, 

 and failed to reach its usual insertion. The anterior fibres terminated mid-laterally 

 on the hyoid arch about half way down this cartilage and opposite the dorsal border of 

 the posterior extremity of the copulo-quadratus profundus, whilst the posterior fibres 

 terminated opposite the dorsal margin of the posterior soft cartilage portion of the 

 hyoid in the fascia of the dorsal border and dorso-internal surface of the copulo- 

 quadratus superficialis. 



It is difficult, as P. Furbringer says, to assign a satisfactory function to this small 

 muscle. Furbringer regards it as a vestigial muscle representing a functional 

 branchial muscle at a time when the first branchial arch was not fused either with the 



* l,p. 332. 



