880 Dr. A. Giinther on Sexual Differences 



head, 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 are 

 similar in form and parallel 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 vi^ith a short ridge 

 projecting into the choana, and armed with two irregular den- 

 ticulations. The intermaxillary is lost. The maxillary bone is 

 very 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-f 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/emfl/e(Pl.XV.figs.B.&C.) is the largest among 

 the Tailless Batrachians, even larger than that of those species 

 such as Bufo agua, 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. Owen (Osteol. Catal. i. p. 121) describes the maxillary bones of 

 Ceratophrys as edentulous ; but the skeleton from which the description 

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

 is also refeiTcd to Ceratophrys, to another South American species of Bufo 

 — probably to Bufo {Otilophus) margaritifer, male. 



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

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

 fied. The peculiar structure of the skulls of these Batrachians is briefly 

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



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

 Neuwied, is 2 inches 11 lines only, Wied^ Beitr. i. p. 586. 



