380 Dr. A. Giinther on Sexual Differences 



licacl, and those ascending from the maxillary ; but there remains, 

 near the origin of the process, a narrow and smooth groove lead- 

 ing to the posterior part of the nasal cavity. The vomerine bones 

 cover the greater part of the ethmoid from beneath, and arc 

 similar in form and ])arallel to this bone, being arched, and ex- 

 tending nearly to the extremity of the ethmoidal processes. In 

 the middle of their length they are furnished with a short ridge 

 ])rojecting into the choana, and armed with two irregular den- 

 ticulations. The intermaxillary is lost. The maxillary bone is 

 Aery slightly arched, and tapers where it meets the hypo-tym- 

 panic ; it is armed with a series of teeth, compressed, pointed, 

 and closely set *. The bone itself is smooth ; but there is joined 

 with it a tubercular dermal plate, which covers the whole cheek 

 and is in immediate contiguity with the broad mastoid process ; 

 it is slightly excavated, and exhibits posteriorly a deeper tri- 

 angular groove with elevated lateral ridges. The tympanic bone 

 is most powerfully developed ; a separated hypo-tympanic can- 

 not be distinguished ; its articular extremity and the two apo- 

 physes, which in other frogs are angularly bent and separated 

 from one another, form here one straight broad bone, obliquely 

 directed backwards, posteriorly convex, anteriorly deeply exca- 

 vated ; the articular extremity has two prominent condyles, with 

 a groove between; the pterygoid process is broad, and united 

 with the maxillary without the slightest suture; finally, the 

 mastoid process, 3'" broad, extends downwards to the maxillary, 

 thus completing a bony ring for the eye, and separating from 

 the orbit another elliptical free space {fossa zygomatica). A 

 similar structure is known in Cultripes provincialis-\ and Calyp- 

 tocephalus Gayi, respecting which I shall have more to say in the 

 course of this paper. The mandibular is lost. 



The skull of the/ewff/e(Pl.XV.figs.B. &C.) is the largest among 

 the Tailless Batrachians, even larger than that of those species 

 such as Bufo a^wa, which surpass Ceratophrys dorsata in the size of 

 the body ; it is nearly three times as large as that of the male, and 

 relatively somewhat shorter and broader ; its greatest breadth is 

 a little before the articular extremities of the tympanic bones, and 

 amounts to 41'" J, its greatest length to 25'", its greatest height 



* Prof. Oweu (Osteol. Catal. i. p. 121) describes tlie maxillary bones of 

 Ceratophrys as edentulous ; but the skeleton from which the descrijition 

 was made belongs to Bufo agua, — and the other smaller skeleton, which 

 is also referred to Ceratophrys, to another South American species oi Bufo 

 — probably to Btfo {OtUophus) marguritifer, male. 



t Pelobates fuscns does not exhibit a temporal arch or an externally 

 closed orbit; therefore the separation into two genera appears to be justi- 

 fied. The ])eculiar structure of the skulls of these Batrachians is briefly 

 mentioned also in the ' Erpetologie gencrale ' of Dumeril and Bibron. 



X The greatest breadth of the skull of a female, observed by Wied von 

 Neuwied, is 2 iuches 11 lines only. Wied, Beitr. i. p. b)i6. 



