256 MR. W. K. PARKER OX THE STRUCTURE AND 



represented by the suddenly narrowed part of this band, which runs back as tlie pith 

 of the long oval palpus, right and left — a " feeler" or barbel wliich reaches to the end 

 of the abdomen. The lower labials are small, niuaded rods, placed across the space 

 between the long, slender mandibles, and ni)t arranged as a semicii-cle to support a 

 sucking disL The hyoids are very massive ; and the branchial pouches are all fused 

 together into a case, with mere slits outside — through which the branchial tufts do not 

 protrude ; and with wider openings inside. 



The larval chondrocranium of I'ipa is similar to that of Dactylethra, but differs in 

 several particulars (ibid., Plates GO, Gl). The auditory capsxdes and cranial notochord 

 reach almost half way to the frontal wall. The trabeculte are completely fused up to 

 their retral cornua. The "sub-ocular fenestra" is a mere crescentic slit with its 

 convexity outwards. The pterygo-palatine band is naiTOW and very small in front of 

 that slit, and the pre-palatine projects forwards under the dilated end of each hook- 

 shaped trabecular cornu. The nasal openings are nearer togetlier; the quadrate condyles 

 are wide apart but not so far forwards in position ; the pedicle is merely the inner and 

 posterior horn of a four-winged, dilated, suspensorium ; the otic process is, ah-eady, 

 nearly as wide as the pedicle, and longer. 



The condyle for the cerato-hyal is a large outwardly-pi-ojecting, oblique, pyriform 

 process ; over it there is a small orbitar process. The labials are scarcely chondriiied 

 as yet, and there are no palpi ; as in M((n, and the Pig, the Meckelian rods meet and 

 coalesce, directly ; and I find no inferior labials. The cerato-hyals are large, oblong, 

 square above, and with a binder submesial process ; they are entirely absorbed before 

 hatching. 



Scarcely a trace of braucliiai appear ; tlie intra-branchial arches are merely repre- 

 sented by a basi-hypobranchial band which, at the mid line, unites the extra-branchials. 

 These are continuous above and below, and form a fiat plate on each side with three 

 lanceolate slits in it, and a dentated upper margin : this growth has its upper part 

 largely absorbed on eitlier side before hatching ; at which time a very remarkable hypo- 

 baslbranchial tract has developed, which in the early larva was merely a conj ugational 

 band uniting the extra-bi'anchials.'^ 



C. — Order of ajypearaiice of parts in the skidl during metamorphosis in the 



" Phaneroglossa." 



The first sjilint-bone to appear in the Tadpole's skull is the first we find in the 

 gradation of the types, viz. : the parasphenoid, 7fr*'i sec/(, outside the merely "Cartila- 

 ginous " Fishes, in the Acipenserid;^ and the Dipnoi. 



The former have no ex-occipital, but the latter have ; this endoskeletal bone comes 



* For tlic transformation of these two extraordinary types of larval crania, I must refer to tlic former 

 paper (Part II.); I still have to show how the adult skulls of the AijJussa differ from those of typical 

 FlMiicroijlvs^a. 



