CCELACANTHDS LEPTUKUS. 17 



The pectoral arches are strong and broad, and have somewhat 

 spatulate upper ends ; they exhibit no sculpture. 



Some points in the structure of the skull are so well displayed in 

 this specimen that I have given an enlarged view of it in fig. 2. 



The posterior moiety of the roof of the skull(^t) meets the anterior 

 at an obtuse angle, and exhibits no trace of sutures. The outer 

 surface of this, apparently single, bony shield is ornamented with 

 minute oval tubercles of enamel, which, posteriorly, run together 

 into short ridges. Very little of the anterior moiety of the roof of 

 the skull is preserved, but so much as remains shows a similar 

 ornamentation. 



The right operculum ( Op.) is broad and triangular ; its surface is 

 marked by ridges, which take a radiating course from its anterior 

 superior angle. These ridges are rather more interrupted, and as it 

 were tuberculated, than they are shown to be in the figure. 



Between the dislocated operculum and the suspensorial apparatus 

 for the lower jaw, several ossified branchial arches {Br.) are 

 visible. 



The suspensorium itself consists of a closely united hyoman- 

 dibular (H.3I.) and palatoquadrate (P. Qu.) portion. The latter 

 is a triangidar strong plate of bone, and its downwardly and 

 backwardly directed apex ends in a stout condyle for articulation 

 with the mandible. Its upper edge is sharp and free, and its an- 

 terior thinner angle becomes connected with the skull, but, in 

 what manner, the state of the specimen does not enable me to say. 



The hyomandibular portion of the suspensorium is, inferiorly, 

 covered by the palatoquadrate, but above, it appears, to be stout 

 and prismatic. External to the anterior two-thirds of the outer edge 

 of the palatoquadrate, what appear to be the remains of a maxilla 

 are "visible. 



Emerging from beneath the anterior attachment of the palato- 

 quadrate, there is a small process of bone which enlarges at its free 

 end 'd). A similar process, apparently developed from the prefrontal, 

 is seen in Macropoma and Undina. In front of this, obscure traces 

 of one or two sharp pointed teeth are visible. 



The impressions of the right ramus of the lower jaw, and of 

 one of the displaced jugular plates ( G) are to be seen below the 

 head. 



This instructive specimen (like the others, unless the contrary 

 be stated,) was obtained from the Coal measures of Pendleton by 

 Mr. Molyneux, and is now in the Museum of Practical Geology. 



No. 2. The specimen represented in PI. Ill %i Jigs. 1., la., lb. 



This is a figure, magnified to twice the natural size, of a small 

 Cceiacanthus lepturus, not more than three and a half inches long, 

 and so disposed as to display the unusually perfect caudal extre- 

 mity very well. 



The skull is about 0-7 in. long ; and, posteriorly, where it is much 

 crushed, it has about half that width. 



It i3 seen from below, and the interspace between the rami of 

 the mandible (a, a) is occupied by the two broad and elongated 

 16295. b 



