DEVELOPMENT OF TUE SKULL IN THE BATRACHIA. 26 J 



in Xenophrys monticola and in Pijxt, or its apex may coalesce with the pedicle, as 

 in Phyllomedusa and Acriti; but as a rule it is confluent above. 



In Callula, Diplopelma, and Engystoina, the basi-hyobranchial plate is sub-carinate 

 below, and a basi-branchial bone appears between the thyro-h}als; in Ahjtes and 

 Pelodytes, a V" shaped splint is applied to this part below. 



In the genus Phryniscus the basal plate is almost as narrow as in Fishes ; its 

 postero-lateral processes are ossified in Bombiimtor, and the cerato-hyals have two 

 saiall centres in them on each side, in Pelohates ; in the two last, and in some of the 

 " Hylidas," the front notch is k(j lar<(e as to make the basal plate like two parts 

 united by a conjugational band, behind. 



In Hyla rubra and //. Eivingii the basal plate extends, behind, as the rudiment of 

 an additional basi-branchial piece. 



The "investing bones" show some curious variations in this group. The para- 

 sphenoid has a distinct centre, in front, in Rana pipiens and in R. halccina. 



The vomers are absent in Pipa and Ilylaplesia ; single in Dactylethra ; and confluent 

 with the ossified nasal floor in some Phrynisci (e.g., P. cruciger and P. varius) : they 

 remain distinct in P. Icevis. 



The fronto-parietals are found right and left, as symmetrical bones, and may divide 

 into frontal and parietal for a time ; these soon coalesce again, and in many cases the 

 median suture is lost ; in some cases {Camariolius tasmaniensis, Acris Pickerinyii, and 

 Jiappia hicolor) they are extremely small. 



The nasals are always present ; they are extremely feeble in Dactylethra. 



The septo-maxillaries are very inconstant ; in some kinds, as Pipa, Ilylaplesia, 

 Bufo ornatus, and Rana pipiens, there is a second prse-orbital behind on each side of 

 them ; in the latter a " lacrymal " is also present : in Rana pipiens there is no proper 

 septo-maxillary, but several irregular palato-maxillaries. 



The preinaxillaries are always double, and the maxillaries nearly always articulate 

 with the qiiadrato-jugal to form a perfect cheek bar ; this bar is deficient in the 

 "Aglossa" and in Phryniscus hvvis ; m Phryniscus the investing bones are very 

 unequal, right and left; and in P. varius and P. cruciger the cheek is scarcely 

 finished ; the quadrato-jugal is suppressed in Pipa. 



The squamosal is remarkably modified in the Aglossa, being hollowed out to help to 

 form the drum-ca\-ity in Pipa and having its lower part aborted in Dactylethra. The 

 hollowing out of the squamosal under the " annulus," is seen again in Ilylaplesia, and 

 more or less in many kinds. Its postorbital process is, at times, very short, in others 

 very long. 



In Dactylethra, only, have I found any rudiment of the bony " annulus tympanicus," 

 it has two ossicles of this nature on each side ; and it only has a single vomer. 



The dentary in the " Phaneroglossa " constantly grafts itself on tiie inferior labial 

 after that has become fused with the distal end of the IMcckelian rod. 



