1862.] OP LEPIDOSIREN ANNECTENS. 131 



extending as far back as the occiput is certainly not much more 

 astonishing than that the frontals should do so. Anj^how, this sin- 

 gular disposition of parts is altogether unique ; but in determining 

 these elements to be frontals I am again guided by the centres of 

 ossification, and especially also by the relative position of the bases 

 of the bones. In this situation it will be noticed that they are con- 

 joined in the middle line, whilst their lateral margins in front are 

 directed at first outwards so as to form the upper part of the incom- 

 plete orbital ring. Viewed as a whole, these bones have been justly 

 compared to a pair of homs ; and their presence, more than any other 

 of the osseous elements, imparts to the skull its unique character. 

 It should be mentioned that the under surface of each bone presents 

 near the inner border a well-defined longitudinal ridge, evidently for 

 the firm attachment of the masseto-temporal muscles. 



Immediately in front of the foregoing, there occurs a solitary bone 

 having the form of an isosceles triangle, whose base is connected by 

 ligaments with the anterior margin of the combined frontals. This 

 bone (K, figs. 1, 3) is regarded by Natterer and Bischoff as the repre- 

 sentative of the intermaxillary — their opinion being grounded on the 

 circumstance of its supporting a pair of incisive teeth (L) at its ante- 

 rior inferior surface. It is impossible, perhaps, to speak confidently 

 on this point ; but I may observe that the teeth in question are not 

 actually implanted in this bone, but are moveably connected with it 

 by ligamentous substance. I regard this fibrous matrix as homolo- 

 gous with the absent incisive elements (or intermaxillaries) ; whilst 

 the triangular bone from which the teeth depend is the conjoined 

 nasals. I find no trace of the transverse suture described by Bischoff 

 as occurring in Lepidosiren paradoxa ; but the tip of the bone in 

 front and above is marked by a well-defined oval surface, roughened 

 for the attachment of the thick cranial fascia. 



Below the above we find a remarkable bone, which, at first sight, 

 appears to be the upper jaw (M). Functionally, indeed, as acting 

 in antagonism with the lower jaw, it may be so regarded ; but mor- 

 phologically and homologically it is clearly referable to the associated 

 palatine bones, which are here of enormous size, intimately blended 

 in front, and widely separated behind. Either division is extended 

 in front so as to form three tooth-like projections, each of which is 

 protected by a thick coating of enamel, the whole constituting a 

 dental apparatus of the most formidable character. In the closed 

 condition of the mouth these teeth become dove-tailed with the 

 interspaces resulting from the similarly formed dentition of the jaw 

 properly so called, the anterior palatine tooth-processes being then 

 placed anterior to the corresponding dentations of the lower jaw. 

 This arrangement is very peculiar ; and its singularity is not lessened 

 by the circumstance that the incisive teeth, above alluded to, have 

 no antagonists. The true maxillary bones have no existence — a defect 

 which, as Miiller and Bischoff observe, also obtains in Proteus, The 

 lip-cartilages, described by the latter author as occurring in L. para^ 

 doxa, I have not found to be present in this species. 



The jaw proper (N) consists of several elements, as in reptiles 



