544 MR. T. GOODEY ON THE SKELETAL [Mar. 15, 



b. Labial Cartilages. 



These were not found by Carman, but Furbringer (6) has de- 

 scribed and figured them, and my observations agree well with his. 

 On each side of the head there are three small, rod-like cartilages, 

 two dorsal and one ventral to the mouth. The ventral one is the 

 longest and meets the posterior dorsal one at the point of the 

 angle of the mouth where both are united by ligament. The 

 dorsal one of this pair is about two-thirds the length of the ventral 

 one and is somewhat inwardly directed. The anterior dorsal one 

 is distinct from those just described. It lies at the posterior end 

 of a ligament which stretches beneath the orbit from the outer 

 ridge of the preorbital process to a point beneath the postorbital 

 process. It is very thin and at its anterior end is also inwardly 

 directed. 



c. First and Second Viscercd Arches, Ligaments and Muscles. 



The suspension of the jaws is hyostylic. At its proximal end 

 the hyomandibular articulates with a rather deep concavity on the 

 auditory capsule. As Carman has pointed out, this articulation 

 does not take place with the whole of the head of the hyoman- 

 dibular, the latter having an oblique disposition to the skull. 

 Thus, only the knob on the posterior side is in contact with the 

 skull, and between the projecting anterior knob and the concavity 

 there is a thick pad of capsular ligament. Garman has also given 

 an accurate description of the general shape and disposition of the 

 hyomandibular. It is suspended in a backward and downward 

 direction at an angle of about forty degrees from the skull by a 

 strong ligament which has its origin on the ventrolateral surface 

 of the auditory capsule. The ligament is attached to this region 

 for some considerable distance, and from here proceeds obliquely 

 backward. It lies internal and ventral to the hyomandibular, to 

 which it is attached on the inner side at about one-half the length 

 of the cartilage from the skull. It is post-spiracular in position 

 and coi'responds with the inferior post-spiracular ligament found 

 in the Common Dogfish, Scyllium canicula, as described by 

 Ridewood (27). There is no pre-spiracular ligament in Chlamy- 

 doselachus, and I agree with Carman in not finding a spiracular 

 cartilage, though Fiirbringer (6) has described and figured as one 

 a. minute piece of cartilage which shows hyaline structure in 

 microscopic sections. I have little to add to Carman's account of 

 the upper and lower jaws ; my observations confirm their shape 

 and disposition as recorded by him. 



The joint between these two cartilages is a very interesting 

 one, and was not dealt with in the original description. It is 

 visible only when the jaws are opened to their widest extent 

 (fig. 3). There are two articulations, each of the cup and ball 

 type, one on the outer and one on the inner side of the joint. On 

 the outer or posterior articulation the quadrate forms a broad, 

 rather flattened knob which fits into a slight concavity of the 



