136 MR. W. K. PARKER ON THE STRUCTURE AND 



The wide contrast between this skull and that of Ahjtes is seen at a glance by a 

 comparison of the figures ; it differs from the " norma " in the following particulars : — 



1. The skull, as a whole, corresponds with that of a young specimen of the typical 

 kind. 



2. The occipito-auditory region is quite ossified, showing no distinction of front and 

 hinder centres. 



3. Tiie skull, proper, is very broad behind, and largely unossified in the interox'bital 

 region, the girdle-bone being impei'fect above. 



4. The annulus and Eustachian tubes are small. 



5. Tlie stapes is very large, projecting, and bony. 



6. The columella is arrested ; thei'e is no inter-stapedial segment or ascending process. 



7. The stylo-hyals are confluent above. 



8. The premaxillaries are grafted on to the 1st upper labials. 



9. The vomers are very small and toothless. 



Note — That the highly ossified hind part of the skull is in great contrast with the 

 feebly ossified fore part ; the large size of the stalked stapes is in great contrast with 

 the arrested columella and the feeble annulus. 



Sixth Family. " Bombinatorid^." 

 Genus Bomhinator. 

 33. Bomhinator igneus. — Adult female ; If inch long. Europe. 



The semi-oval skull is of the average form ; the length is as to the breadth as 

 7 to 8, and the quadrate condyles reach to a point opposite the fore edge of the 

 stapes; in Alytes they wei-e opposite its fore edge, but the breadth of the skull was 

 much greater. 



This and the next type have many things in common, but their skulls are in strong 

 contrast, on account of the feeble ossification of the one, and the unusual degree of 

 hardness attained hy the other ; the contrasted figures will show how they difier 

 (Plate 25, figs. 1-4, and 5-11). 



The main difference in form of outline between the skull of Bomhinator and that of 

 the Common Frog, is that in the former the snout is much wider ; the interorbital 

 region is much alike in botli, it is rather naiTOW, lessens from befoi-e, backwards, and 

 bulges gently in the middle. 



The auditory region is also wider, and the whole skull more archaic, and also much 

 arrested. 



The occipital condyles {pc.c.) are separated by an interval their own breadth, and 

 but little emarginate ; they are supcro-iwsterior in position as in Pipa, which is a rare 

 modification. The roof over the foramen magnmn is also gently emarginate, and both 

 in roof and floor the bones (e.o.) are divided by a moderate wedge of cartilage. 



