Dermal Bones of the Skull 



89 



,,apophysis" of the primary dermal bones on which they occur.^^j 

 This is, however, but a presumption or rather supposition on my 

 part, and the question remains to be settled by future, careful 

 investigations, in the course of which special attention ought to 

 be paid to the, as yet unknown, ontogenetical or osteogenetical 

 development of the mentioned armaments. 



In the Ophidian Order no secondary dermal ossifications 

 are known. 



Let US now throw a glance upon the bony dermal armour of 

 some other, more ancestral Reptilian Orders. 



Some Dinosaurs present exoskeletal Clements on the body, 

 which either form a more or less extensive closed armour, or 

 consist but of isolated plates. As regards the skull, the distal 

 portion of the ,,horns" of Ceratopsidae will presumably prove 

 to represent secondary dermal bones, and practically to belong 

 only in their proximal (basal) part to the primary dermal bones 

 (,,membrane" bones) of the skull. ^^) The smaller ossicles on 

 the periphery of their parietal and squamosal bones are surely 

 secondary exoskeletal Clements. — It is most probable that 

 the praedentalbone of the Praedentata {,,Ornithischia") will also 

 prove to be a secondary dermal bone, just like in the case of 

 the homonymiC bone occurring in some Fishes. 



Among the Crocodilians it is especially the palpebral 

 bones (very strongly developed in Caiman palpehrosvis Cuv. and 

 C. trigonatus Sehn, for instance) which are to be mentioned as 

 representing typical secondary dermal bones. These Cle- 

 ments are formed by the corial tissue of the Upper eyelids; 

 C u V i e r *^) records them , with respec ttothetwoCaimans mentioned, 

 as follows: ,,L'epaisseur de la paupiere superieure est entierement 

 remplie d'une lamic osseuse divisee en trois pieces par des sutures; 

 dans tous les autres ca'imans et crocodües, il n'y a qu'un petit grain 

 osseux vers l'angle anterieur." This dement has been figured by 

 Prof. Brühl*^) as ,,supraorbitar*, and by Prof. Gadow^*^) (in 

 A. missisipiensis Daud.) as ,,lacrymar' (O^*^) both homologi- 

 zations being absolutely inadmissible. The same palpebral bone 

 is also present in some fossil forms, as in Nannosuchus for instance. 

 The sculptures, thoroughly obliterating in old specimens the 

 outer (superficial) limit of the Single primary dermal bones, must 

 be considered as a crusta calcarea, i. e, a secondary dermal 



Cfr. the following Statements set forth in the discussion of the 

 Mammalian horiis and antlers. 



Cfr. the preceding footnote. 



S. les düf. esp. de Crocod. viv. &c., Ann. Mus. d'Hist. Nat., Paris, 

 T. X, 1807, p. 37. 



Das Skelet der Crocodilinen, Wien, 1862, and Zoot. all. Thiercl., Wien, 

 Taf. p. VI, 1874 & Taf. p. CXXXIII, Fig. 7, 1886. 



Rept. and Amph., in; Cambr. Nat. Hist., London, 1901, p. 468, 

 Fig. 112. — NB. The „true" lacrymal lies between the praefrontal and the 

 maxillary ! 



VVhat about the true lacrymal then ? 



7. Heft 



