332 



and arteries of embryos, in so far as my material permitted of their 

 investigation. 



The quadrato-palatinus and palato-coronarius muscles are deep 

 muscles that arise respectively, as their names imply, from the so- 

 called pterygo-quadrate and palatine. They run horizontally forward, 

 and are inserted, the one on the palatine, and the other on the lateral 

 labial cartilage or in the tissues near that cartilage. The palato- 

 coronarius is innervated by a branch of the maxillaris trigemini. The 

 innervation of the quadrato-palatinus I could not determine, but 

 Müller says that it is innervated by a branch of the nerve that in- 

 nervates the velar muscles. Fürbringer gives a similar innervation 

 for the corresponding muscle in Myxine. This innervation, however, 

 seems to me in itself singular, and as, moreover, the texture of the 

 muscle fibres of the quadrato-palatinus is markedly different from that 

 of the velar muscles, I think it quite probable that the muscle is 

 innervated either by the mandibularis, or by the maxillaris trigemini, 

 both of which nerves pass close to it, the mandibularis even usually 

 in part traversing it. These two muscles thus might, from their 

 position and possible innervation, be the homologues of the first and 

 second divisions of the levator maxillae superioris of Amia. Those 

 muscles in Amia arise from the anterior edge of the hyomandibular, 

 and not from the quadrate, but this would naturally be the case under 

 the changed conditions. The insertion of the palato-coronarius on or 

 near the ventral end of the lateral labial cartilage, would then seem 

 to indicate that the latter cartilage of Bdellostoma represented a part 

 of the palato- quadrate of Amia. The relations of the ramus maxillaris 

 trigemini to this cartilage are also strongly in favour of this assumption ; 

 for this lateral labial cartilage is the only part of the skeleton of the 

 head of this fish to which these nerves have the relations, lateral and 

 dorsal, that they always have in fishes other than the Cyclostomes. 

 Furthermore, there are two muscles, the copulo-ethmoidalis and copulo- 

 tentaculo-coronarius, that might, if the lateral labial cartilage be a 

 palatine, represent the third and fourth divisions of the levator maxillae 

 superioris. 



The cranio-hyoideus muscle arises from the hind end of the otic 

 capsule and from the notochordal sheath immediately posterior to that 

 capsule, and running outward and downward through the lateral 

 fenestra 3 (Parker) is inserted on the distal end of the ceratohyal 

 (Parker). If fenestra 3 were to become closed, by the fusion of the 

 enclosing cartilages, the muscle would be cut into two parts, an inner 



