IN THE PARAGUAYAN LEPIDOSLREN, ETC. 357 



frontoparietal as far forward as the anterior limit of the periotic capsules, while the 

 exoccipital bones are invested externally, but not internally, by cartilage. In fact the 

 chondrocranium is complete dorsally and laterally in the periotic and post-auditory 

 regions, and would also be so ventrally were it not that the basal cartilage ceases a little 

 behind the middle of the periotic region. The trabecular cartilages are similar to 

 those of Lepidosiren, but of somewhat greater vertical extent in the region immediately 

 anterior to the periotic capsules, and for a short distance behind the junction of the 

 fronto-parietal and parasphenoid they even contribute to the formation of the lateral 

 walls of the cranial cavity (Wiedersheim, I. c. Taf. ii. fig. 5). Precisely as in Lepido- 

 siren, the trabecular cartilages become continuous in front of the anterior termination 

 of the parasphenoid with the persistent and upwardly-deflected basicranial cartilage of 

 this region ; but, again separating from it anteriorly, they diverge outward and down- 

 ward across the outer surface of the palato-pterygoid bone in the form of extremely 

 slender antorbital cartilages. The latter curve downward and backward into the 

 hinder margin of the upper labial fold and there terminate, but without extending 

 forward into its inferior border, or giving off anteriorly-directed processes. The 

 continuity of the trabecular and antorbital cartilages has been described by Wieders- 

 heim (7. c), although, curiously enough, it is not represented in any of his figures. 

 Peters (I. c), however, was the first to show the relations of the two structures in his 

 figure of the skull of a Protopterus from Zambesi, and indeed gives a more accurate 

 representation of the shape and curvature of the antorbital process than any other 

 figure with which I am acquainted. 



From the point where the basicranial cartilage begins to be deflected upward by 

 the palato-pterygoid symphysis the ethmo-nasal portion of the chondrocranium differs 

 but little from that of Lepidosiren, and the figures given of this region in the latter 

 Dipnoid are, in the main, equally applicable to Protoptems. Trabecular cornua, 

 subnasal cartilages, and a bilobed prenasal process are present, and in every respect are 

 almost identical with the corresponding structures in Lepidosiren. In both genera the 

 fenestration of the roof of the two nasal capsules is regular and almost symmetrical. 

 The presence of subnasal cartilages was overlooked by Wiedersheim, although they had 

 previously been figured by Peters (I. c. Taf. ii. fig. 3, Jc'), whose accuracy in this respect 

 I am able to confirm. I notice that Wiedersheim (/. c. Taf. ii. fig. 5) represents that 

 portion of the internasal septum which carries the two vomerine teeth as segmented off 

 from the hinder part of the septum and separated from it by a curved vertical suture, 

 and a statement to the same effect occurs in the text (I. c. p. 52). With reference to 

 this point I can only say that in a skull which I have had the opportunity of examining 

 no such division could be detected, and the septum was continuous throughout its 

 extent. The same figure is also slightly inaccurate in not representing the mesethmoid 

 cartilage which, as in Lepidosiren, is situated immediately behind the palato-pterygoid 

 symphysis. 



vol. xiv. — pakt v. No. 5. — February, 1898. 3 a 



