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Bashford Dean Memorial Volume 



also in Allis's representation (Figure 7, plate II). The angle of the lower jaw literally 

 reaches back behind the skull into the region of the gill'arches. As may be seen in Text' 

 figure 8 from Garman, the lower jaw is, for a shark, remarkably long, narrow and pointed. 

 Furthermore it is rather frail as one may see in Collett's figure (Figure 6, plate II). One 

 could by hand easily break the lower jaw of one of our preserved specimens. 



In marked contrast with the form of the mouth of Chlamydoselachus as seen in all 

 other figures reproduced in this article, and as observed in all our specimens, is that shown 

 in Ito's drawing (1931) reproduced herein as Text-figure 5. The figure calls for no com- 

 ment, save that we are unable to offer any explanation for it. 



The peculiar structure of the jaws has been admirably characterised by Goodey 

 (1910, p. 550) as follows: 



Perhaps the most important point in regard to the specialization of the skull of Chlamy- 

 doselachus is to be seen in the extreme length and mobility of the jaws. These are exceptionally 

 long, extending from the anterior, almost terminal mouth to a point well behind the posterior 

 limit of the cranium. This extension is remarkable; in fact, one quarter of the total length 

 of the jaws is found in this region, and it is this feature, connected with the exceptional 

 length of the hyomandibular, which gives the jaws their great mobility. Indeed, their dis- 

 position relative to the cranium is quite different from that found in any other Selachian 

 whose skull I have been able to examine or to see a figure of. It resembles nothing among the 

 Vertebrates so much, perhaps, as the general disposition of the jaws in certain of the Ophidia. 



In this connection it will be of interest to set forth the measurements of the mouths 

 (Table VII) of our three fish and those of the head from Columbia University. It should 

 first be stated that in our fish the jaws have been hardened shut, and although we have 

 forced them open the measurements are undoubtedly smaller than they would have been 

 in live or in freshly caught fish. On the other hand the mouth of the head from Columbia, 

 preserved open, is probably more widely distended than is natural. 



TABLE VII 

 MEASUREMENTS OF THE MOUTH OF CHLAMroOSELACHUS AHCUIHEUS 



Both upper and lower jaws possess rudimentary lip-like structures. Concerning 

 these AUis (1919, p. 146) says: 



In Chlamydoselachus the lips are much thicker at the angle of the gape of the mouth than 

 in their anterior portions, the angle of the gape thus being a relatively long line. The inner 

 end of this line forms the functional angle of the gape when the mouth is widely opened, and the 

 outer end of the line the functional angle when the mouth is closed and from this outer angle 

 the outer edge of each lip converges toward the inner edge until the lips attain their 



