DEVELOPMENT OF THE SKULL IN THE BATRACHIA. 57 



and 3, sq.), for the descending position of the post-orbital process, and for the bifurca- 

 tion of the suprateniporal plate, embracing the " pterotic " cartilage. 



The quadra to-jugal (q.j.) grafts itself very little ; the maxillary (mx.) has a very 

 distinct ascending facial process below the nasal ; it does not, however, articulate 

 directly with that bone, for there is a small squarish pre-orbital (p.ob.) between them. 



Behind this (Plate 8, figs. 1 and 3, /.) there is an oblong bone, also attached to 

 the descending eras of the nasal (n.) ; this is the "anterior suborbital" or lacrymal ; 

 this is a familiar bone in the Teleostei, and the other is common in one " Family " 

 of that " Order," namely, the "Siluroidei." 



But these are not all the prcster-normal ossicles ; there is no functional septo- 

 maxillary, as in R. temporcma, where it lines the nasal passage, but there are a number 

 of generalised bony points close to where that bone appears, below, in the Common 

 Frog. On the left side (Plate 8, fig. 2, and Plate 9, fig. 7, p.mx.) these are clo.se to 

 t\\e palatal junction of the pre-maxillaries and maxillaries, some larger, and others lesser, 

 " palato-maxillaries ; " on the right side (Plate 8, fig. 2) there are two narrow bones, 

 larger than the largest on the left side. 



These do not make up the whole tale of the additional bones ; the parasphenoid 

 (Plate 8, fig. 2, pa.s.) has at its apex a separate " pro-parasphenoid {pa.s.) as I showed 

 in the larva of this species (Plate 3). This bone is about a quarter the size of the 

 blade of the large bone, which is split where it underlies the new centre. 



The vomers (fig. 2, v.) are large and quadrilobate, yet they neither meet at the mid- 

 line nor reach near to the maxillaries ; for the nasal region, although large really is 

 small relatively to the huge face. The fourth or dentigerous lobe of each vomer is 

 rounded, the two intermediate lobes that enclose the inner nostril are sharp, and the 

 front lobe is crescentic. 



Above (figs. 1 and 3, n.) the nasals are broad, roughly convex, in contact in their 

 hinder part, do not reach the maxillaries externally, and together form a sub- pentagonal 

 roof. Between them, behind, there is an emargination which passes into the notch 

 between the fronto-parietals {f-P-) and exposes some of the girdle-bone {eth.), whose 

 superorbital lobe (s.ob.) is also uncovered externally. 



The frontals are not confluent with each other, but with the parietals ; these are 

 completely anchylosed together (fig. I, /.p.). 



The sides of this roof are almost parallel for two-thirds of the interorbital region ; then 

 the bones suddenly widen, then become pinched and bi-cristate, and then double their 

 breadth over the inter-auditory region, where their outer margin is emarginate, and 

 their surface sinuous over the double " canal." The two crests are divided by a fossa ; 

 they are first temporal, and then sar/ittal. 



This compound roof ends, behind, in a transverse, dentate, squamous edge, leaving 

 the narrow superoccipital region uncovered. Laterally (fig. 3), the bony roof and the 

 bony floor are seen to be modelled over and around the endocranium, hiding half 

 of it. 



MDcrrr.xxxr. r 



