79G REPORT OF COMMISSIONER OF FISH AND FISHERIES. [50] 



A large azygos gular plate partially fills in the inter-ramal space (PL 

 VI, Fig. 20, G. pi.). This plate, occupying as it does the same position 

 as the paired structures of similar description in Polyterus, is held to 

 the surrounding bone by the skin and other soft parts. Its anterior 

 end develops an expanded tip, which is connected by stronger liga- 

 ment to the symphysis of the jaw. Externally, the surface is sculpt- 

 ured like the ganoid plates on the roof of the skull, while its internal 

 surface is quite smooth. The homology of this plate is still unsettled. 

 It has been spoken of as replacing the urohyal. A very long, osseous 

 gular plate is found in the inter-ramal space among the Elopidse. 



Of the Cranium. — So minutely has Dr. Sagemehl described this part 

 of the skeleton of Amia calva, that I will here but hastily view the 

 points for examination, and introduce them merely as a recapitulation 

 to fill in my own account of the skull. 



To examine the cranium we must take the head of a fresh specimen, 

 remove the shoulder-girdle, all the ganoid plates, and other structures 

 below and laterally that do not belong to it. Then, from a superior 

 view, we have presented us for examination a Jarge, central quadrilat- 

 eral, cartilaginous track (Fig. 6). At the anterior extremity of this, we 

 see the intermaxillary (Sm.) ; the premaxillary [Pmx.), and the prefrontal 

 {Prf.). Occupying a lateral and at the same time a mid position we see 

 the postfrontal (Fig. 6 Fsf.), while it is bounded behind by the opisthotic 

 at the outermost angle (Fig. QJc, intercalare, Sagemehl, op. o, opisthotic 

 of Bridge), just within which, and above it, we find the exoccipital 

 (Ex) — this latter is marked ep. o. in Bridge's figure, he considering it 

 the epiotic. Behind these two bones we observe in Fig. 6 a segment 

 marked 01, this is the occipitale later ale of Sagemehl, and the exoccipital 

 of Bridge. To the rear of this again we find the occipital arches, so 

 well described by the former author in Part I of this paper. 



Now, turning the cranium over, we have presented us upon its infe- 

 rior asi^ect, for examination (Fig, 2), first, the pair of vomers (vo.), situ- 

 ated anteriorly ; then traversing the basis cranii longitudinally the para- 

 sphenoid Fs. {pa.s in Bridge's figure). An almond-shaped area in the 

 middle of this latter bone is covered by fine teeth, while the anterior 

 thirds of the vomers support others which are very much larger and ar- 

 ranged in a circular grouj). The vomers and parasphenoid must now 

 be carefully removed ; then we have before us the ossifications shown 

 in Fig. 3— the base of the cranium. Proceeding from before back- 

 wards, there are the premaxillary (Pmx.) ; the septo-maxillary (Smx.) ; 

 the prefrontal (Prf.); the orbito-sphenoid {Os.); the alisphenoid (As.); 

 the postfrontal {Prf.) ; i3etrosal {Pe.) (the prootic of Bridge) ; the opis- 

 thotic [Jc.); and the occipitale laterale {01.) spoken of above. The infe- 

 rior view of the co-ossified occipital vertebrae is also to be seen from 

 this side. 



Upon a direct lateral view (Fig. 5) may be seen the premaxillary 

 {Pmx.) ; the septo-maxillary {Sm,x.) ; the prefontal {Prf.) ; the orbito- 



