Die Zähne am Rostrum der Pristiden. 59 



of calcig-eroüs tubes blending together near the point where the 

 two contiguous medullary canals were about to inosculate. 



The reticulate arrangement of the calcigerons tubes is more, 

 and the radiated one less, conspicuous in the rostral teeth of Pristis 

 than in the teeth of any other species which I have yet examined. 

 The diameter of the calcigerous tubes at their origin is Veooo^h of 

 an inch, their terminal branches may be traced to the minuteness 

 of ^'2ooooth of an inch. 



In the embryo of a Pristis six inches long, to which the um- 

 bilical chord was still attached, I found a series of depressions in 

 the skin along the margins of the rostral prolongation corresponding 

 in number and relative position with the future teeth; and at the 

 bottom of each of these dermal follicles, there was a papilla which 

 formed the apex of a pulp, whose base had already begun to pene- 

 trate the cartilaginous plate of the rostrum. The pulp had the 

 usual dense and unyielding external „membrana propria", and its 

 apex was covered by a continuation of the tegumentary follicle of 

 extreme thinness, but there was no true capsule or enamel organ. 

 The calcareous particles had not begun to be deposited in the tissue 

 of the pulp. 



The teeth of the j'oung specimen, of which the head and saw 

 are figured in tab. 8, fig. 1, were fully calcified, and except that the 

 number of medullary canals were fewer, and the deportion of the 

 calcigerous tubes greater, they were in every respect miniature 

 resemblances of the teeth of the full grown fish, such as are figured 

 of the natural size at tab. 8, fig. 3 and 4. 



Diese in den Einzelheiten der Beobachtung überall zutrefî'enden 

 — wenn auch hinsichtlich ihrer Deutung mancher Änderungen be- 

 dürftigen — Ausführungen begleitet Owen mit einer Reihe sehr 

 schöner und genauer Abbildungen. Besonders die figg. 3 u. 4, tab. 8 

 und fig. 2, tab. 9 sind als bemerkenswert hervorzuheben. 



In der GiEBEL'scheu Odontographie (1855) werden die Zähne 

 am Rostrum von Pristis ebenfalls kurz erwähnt: 



„Er besitzt ... in dem sägeartig verlängerten Schnauzenteil 

 jederseits eine Reihe eingekeilter, schlank und stark komprimierter 

 kegelförmiger Zähne, deren Vorderrand abgerundet, deren hinterer 

 eine entsprechende Längsrinne hat. Zur Hälfte ihrer Länge stecken 

 sie in den Alveolen." 



Zuletzt kommt er auf die Verschiedenheiten der Zähne bei den 

 einzelnen Arten zu sprechen. 



