206 ON THE STRUCTURE OF THE SKULL. 



the prefrontals, G, G to the post-frontal, B, B to the epiotics, 

 and A to the supra-occipital of the Pike. But every one of 

 these is a membrane bone, and not, as are the corresponding 

 elements of the Pike's skull, a cartilage bone. 



These bones are therefore, strictly speaking, the analogues, 

 and not the homologues, of the bones to which they appear to 

 answer in the Pike, though hitherto no distinction has been 

 drawn between the two. 



K and I, 1 are bones which do not properly belong to the 

 skull, but which, as happens among many Siluroid Teleostei, 

 are anchylosed with the cranium. K is the most anterior 

 of the median dermal scutes, and 1, 1 are the supra-scapular 

 bones. The letters L, L indicate the scapular bones move- 

 ably united with these last. 



The suspensorium of the Sturgeon consists of a large, irre- 

 gularly-prismatic body, composed of a bony central piece (/, Fig. 

 83) with two cartilaginous epiphyses, the lower of which (g) is 

 much the longer, and is connected by ligament with another 

 cylindrical cartilage (Ji), while the upper articulates with the outer 

 and under part of the auditory capsule. Bather above the letter 

 h, the lower cartilage gives attachment to a cartilaginous nodule 

 with which the principal piece of the hyoidean arch is connected. 



At its distal end the cylindrical cartilage (h) is united by 

 ligaments to the two apparatuses h and Mn. Of these, h may 

 be described as a rhomboid, composed partly of cartilage and 

 partly of bone, and so bent as to assume a transversely arched 

 form. Its outer angles present convex articular meets to con- 

 cavities on the lower arch (Mn), which last, composed of a 

 single bony ramus on each side, is undoubtedly the mandible. 



Fig. 83. 



Fig. S3. — Side view of the cartilaginous cranium of Accipenser (after Miiller). — a, 



truin ; 6, nasal chamber; Or, orbit; c, region of the auditory organ ; /, g, h, sus- 

 pensorium ; k, maxillo-palatine apparatus ; Mn, mandible. 



