in the Bones of some Frogs and Fislies. 381 



to 17'". It differs from the skull of the male in the following 

 details : the foramen occipitale magnum is relatively broader and 

 lower ; the process of the exoccipital is compressed, and projects 

 as a rather sharp ridge ; the crest of the external superior portion 

 of the OS petrosum is much more developed, and elevated above 

 the level of the skull, whilst the bridge which separates the orbit 

 from the fossa temporalis is not much broader than in the male. 

 The vertex is relatively narrower, and the interspace between the 

 eyes more excavated ; likewise the whole cavity of the mouth, 

 viewed from beneath, is more concave and deeper. The maxillary 

 bone is equally broad in its whole length, and exhibits an obsolete 

 suture where it meets the hypo-tympanic; the tympanic bone is 

 bent more outwards ; and the fossa zygouiatica is larger, irregu- 

 larly four-sided, anteriorly with an obtuse angle, and posteriorly 

 with an acute one. The orbit is relatively much smaller. The 

 anterior part of the facial bones is lost. 



All these differences — differences of form — are exactly the 

 same as between the male and female of the living species. For 

 the purposes of future comparison, the following dimensions are 

 added : — 



Male. Female, 

 lines, lines. 



Greatest length of til e skull 18 25 



breadtli of the skull 24^ 41 



„ height of the skull !ii 17 



Depth of the foramen occipitale magnum 2 2 



Width of the foramen occipitale magnum 2\ 3| 



Greatest distance between the fossae temporales 8 10^ 



Smallest distance between the orbits 4j 7 



Distance between the foramen occipitale magimm and the 



extremity of the ethmoid 13^ 20| 



Breadth of the bridge between fossa temporalis and orbit . \\ If 



„ „ „ fossa zygomatica and orbit . 3 5 



„ „ „ „ ,, and temporalis 5^ 8 



„ „ „ orbit and nasal opening ... 2 41 



Diameter of the orbit 5| 6f 



Distance between the outer extremities of the palatine bones 14^ 25 



The peculiar and solid structure of the skull of Ceratophnjs, 

 deviating from most of the Tailless Batrachians, is in immediate 

 connexion with the mode of life of these large frogs. They are 

 said to feed on other frogs, on birds, mice, young rats, &c. * : 

 I myself found, in the stomach of one of these animals, an en- 

 tirely uninjured Cystignathus ocellatusi half the size of its de- 

 stroyer. It is reported by Dalton that frogs were successfully 

 introduced from the continent of tropical America into some of 

 the West Indian islands, because they were known to be very 

 useful destroyers of the rats. I think that the Horn-frog is much 



* Wied, Beitrage, i. p. 589. f Dum. & Bibr. viii. p. 43/. 



