Osteology of the Head of Ilatteria. 301 



the entire side of the jirocess and is united with tlie occipital 

 part by only partly distinct sutures." The paroccipital 

 described by me t'ornis the posterior wall of the labyrinth and 

 sends the processus paroticus outwards. It is consequently a 

 bone of considerable importance, separated by a suture from 

 the pleuroccipital. Only on the posterior surface of the par- 

 occipital does the suture between it and the ])leuroccipital 

 remain indistinct at a spot which is of quite small extent, so 

 that here the two bones appear to be united by synostosis. 

 It may be that the specimens which I examined were not 

 sufficiently young in order to siiow the complete separation of 

 the bones in question. I was able, nevertheless, in the crania 

 of three individuals to perceive distinctly the suture between 

 paroccipital and pleuroccipital, which sepai'ates the two bones 

 one from another with the exception of a small space, so that 

 the possibility of a merely individual separation of these two 

 bones seems to be excluded. 



I imagine that Glinther j)robably identified the paroccijutal 

 correctly, but the sutures in the specimen investigated by 

 him were no longer sufficiently distinct to enable him to 

 recognize the precise limits of the bone in question. He says, 

 moreover, in a note (lac. cit, p. 2) : — " The sutures between 

 these bones [namely between supraoccipital and exoecipital] 

 are so indistinct that they could not be represented in the 

 drawing." It is tiie more remarkable that Briihl {loc. cit.) 

 did not perceive the division between the paroccipital and 

 pleuroccipital, since nevertheless he figures and describes the 

 head of a young individual in which all the sutures between 

 the several bones of the occipital and sphenoid grou[)s were 

 still distinctly visible. He assumes an attitude of vigorous 

 opposition to GUnther's alleged paroccipital : — " The pleur- 

 occipital is, as I must maintain in opposition to an 



absolutely incorrect statement on the part of Giinther [loc. cit. 

 p. 596), the only lateral element of the occipital segment in 

 Hatteria ; no other element, no exoecipital \)nilii^ paroc, 

 Owen, opisth. of English authors] exists at all. Giinther's 

 statement that a paroccipital of Owen [exoecipital, mihi^ is to 

 be found in Hatteria is based upon an extremely superficial 

 inspection, erroneously conducted upon entire preparations (!), 

 which, however, was not supported by any more precise 

 investigation (disarticulation ! the only anatomical methcid 

 which IS here conclusive)." As is evident from my descrip- 

 tion, Briihl was entirely in the wrong in disputing GUnther's 

 statement ; the paroccifMtal is present in young individuals, so 

 that consequently Hatteria , like the Chelonians, exhibits six 

 occipital elements, namely: — 1 basioccipital, 1 supraoccipital, 



