Dermal Bones of the Skull 



85 



genesis of the pilear shields in general, and to discuss il, and to 

 what an extent, their shape might be dependent on blood-vessels. 

 1 should merely like to suggest that the outlines of the elements 

 of the secondary dermal ossifications agree, as a rule, with those 

 of the pilear shields, and that just the contrary of Prof. Leydig's 

 Statement seems to occur : it is not the shape of the pilear scutes 

 or shields, occurring in all Reptiles, which depends on that of the 

 corial ossif ication, present on the skull of certain groups, 

 but these latter ones are secreted (by the corial tissue) within 

 the separate fields of the single shields, the morphology of 

 which draws, in a quasi mechanical way, the limit between the 

 settling groups of lime-concretions, i. e. between each secondar}/ 

 exoskeletal plate or surface of ossificaticn. 



In 1886 Prof. Brühl dealt with the elements here dis- 

 cussed. Mr. Siebenrock^^) resumes Brühl' s respective views 

 in the following terms: ,,Wie aus seiner Darstellung zu schliessen 

 ist, hält er die Knochenkruste oder den Hautknochenpanzer der 

 Lacertiden für ein Gefüge von selbständigen Kncchenplatten, 

 welche nicht mit der Oberfläche des Schädels verwachsen, sondern 

 ihr nur angeklebt sind. Sie können daher, wie Brühl glaubt, wenn 

 auch nicht leicht und nicht immer gleich gut, vom Schädel los- 

 präpariert werden." 



In 1894 the famous Vienna Anatomist, Mr. F. Siebenrock, 

 of the k. k. Naturhistorisches Hofmuseum, published the result 

 of his observations on the skeleton of Lacerta Simonyi Steind. 

 and on that of the Laceriidae in general. In this highly valuable 

 paper the author devotes p. 223 — 225 to the description of the 

 crusta calcarea. According to him this incrustation, which is 

 present in some Saurian f amilies, as ,,bei den Scincoiden, Anguiden 

 und Gerrhosauriden", would be especially developed in the Lacer- 

 iidae. I cannot agree with this opinion, because, asstated above, the 

 secondary dermal ossifications are much more developed in Ophi- 

 saums {Anguinidae) , Trachysaurus, Tiliqua, Egernia (Scincidae), 

 Zonums (Zonuridae) or Heloderma ( Helodermatidae) than in the 

 younger representants {Laceriidae) of thesame (i. e. tect orbital) Type. 



Mr. Siebenrock emits the opinion that, with respect to the 

 interpretation of the exoskeletal ossifications, Brühl's statement 

 is wrong. He writes as follows^^) : ,,Alle Versuche, die Knochen- 

 kruste oder nur einen Theü derselben von der Schädeloberfläche 

 loszutrennen, bleiben erfolglos. Dass man die Knochennähte am 

 Schädel deutlicher hervortreten sieht, wenn man die schrundigen Er- 

 habenheiten mit dem Messer oder Schaber entfernt, ist ausser 



Zootomie aller Thierclassen, Taf. p. CLI, with Explanation, Wien, 



1886. 



31) 1. c. 



Op. cit. — In his earlier publication ,,D. Kopfskel. d. Anguiniden, 

 Scincoiden u. Gerrhosauriden", appeared in the Annais of the Vienna 

 Natural History Hofmuseum, M. Siebenrock does not deal with the 

 elements we are discussing. 



Op. cit. p. 224-225. 



7. Heft 



