1910.] ANATOMY OF THE FRILLED SHARK. 545 



posterior and outer end of the mandible. The inner or anterior 

 articulation is formed by a prominent rounded protuberance — 

 somewhat more than half the width of the one on the quadrate — 

 which projects upwards into a corresponding concavity or facet in 

 the quadrate. 



This joint affords a resemblance with Heptanchus, the corre- 

 sponding joint in which has been worked out by Gadow (8). There 

 is the difference, however, that in Ghlamydoselachus it is much 

 more pronounced and has not the space separating the two 

 articulations found in Heptanchus. Garman mentions a palatal 

 or trabecular process which occurs at a point an inch and 

 three-quarters behind the front end of the palatoquadrate, and 

 is received in a concave articular depression of the skull in the 

 orbit. He says that it is attached at its upper end by ligament 

 to the skull near the top of the orbital cavity. I have found the 

 process in question in both skulls that I have examined. It is 

 perhaps better to call it an ethmo-palatine process, this being 

 in accord with modern nomenclature. I cannot, however, agree 

 with Garman in what he says about its ligamentous attachment 

 to the skull. It is not attached by any definite band-like ligament 

 such as that figured by him on PI. viii. It is surmounted by a 

 pad of capsular ligament which appears to be in the nature of a 

 thickening of the general soft connective tissue surrounding the 

 whole pr-ocess. A similar capsular ligament has already been 

 described as occurring between the obliquely placed head of the 

 hyomandibular and the articular concavity on the side of the 

 auditory capsule. Both are very different from the strong, 

 fibrous, band-like post-spiracular ligament which suspends the 

 jaws from the skull. 



I have found the hyal process which occurs on the upper ridge 

 of the quadratic portion of the upper jaw, close to its posterior 

 end, overhung by a similar one on the hyomandibular. The 

 larger quadratic or otic process however, which, according to 

 Garman, occurs farther forward at the widest part of the palato- 

 quadrate, I have failed to discover. 



The ceratohyals articulate by the anterior lobe of their lower 

 extremities with the ventral surface of the basihyal, on either side 

 of the median line. The latter cai-tilage is situated well forward 

 between the mandibles and is raised up slightly into the oral 

 cavity. As Garman has pointed out, it is elongate and tapers 

 from the broader posterior end to the rounded anterior end. In 

 the middle of the concave posterior border is a small, backwardly 

 directed prominence, which JFiirbringer (6) considers as the repre- 

 sentative of the copula or basibranchial of the first branchial 

 arch. The two lateral prominences, also at the posterior end, no 

 doubt represent the hypobranchials of the first branchial arch as 

 Garman suggested, and these together with the basibranchial 

 have lost their distinct nature by becoming fused into the general 

 mass of the basihyal. 



On the ventral surface of the basihyal is found the somewhat 

 Proc. Zool. Soc— 1910, No. XXXY. 35 



