38 MR. W. K. PARKER ON THE STRUCTURE AND 



respects it corresponds with the Oriental Frogs, and differs from most of those of the 

 Nearctic and Pahoarctic regions; this is seen in the presence of an "anterior super- 

 orbital" expansion of the chondrocranium (Plate 5, fig. 1). 



This is an unusually narrow and elongated skull, and thus differs from that ot 

 R. inpiens which is short and wide ; the last was elongated but did not narrow in so 

 much in front. This sub-triangular form, the relatively elongated nasal region, and the 

 gradual, but great, widening from before backwards of the cranial " barge," are very 

 characteristic things in the skull of this species. Add to these the rudimentary super- 

 orbital plate in front at the narrow end of the skull, the wide temporal region, the 

 heart shaped great fontanelle, and the small lesser fontanelles, and we get a number ot 

 things worth notice. Yet these are of secondary morphological importance, their value 

 is lai'gely Zoological and Taxonomic. In the nasal region we see that the outer angle of 

 the " subnasal " cartilage {s.n.l.) has formed a retral lobe — a part very distinct in the 

 adult i2. temporaria. The pro-rhinals [p.rh.) are rather retral than out-turned; the 

 upper and lower cartilaginous laminae are curiously alternated as to their wide and 

 narrorv ends ; the upper is narrow in front, and the lower wide, and vice versd. 



The bending of the palato-pterygoid " bow " is greater here than in the last, and 

 the proper suspensorium is modified by the more backward position of the quadrate 

 condyle (q.c), by the fusion of the otic process with the " tegmen tympani " (fig. 1, 

 between the letters a.s.c. and h.s.c), and the greater perfectness of the articular facet 

 of the pedicle (pd.). 



The ex-occipitals (e.o.) are now large, and leave only a narrow oblong basioccipital 

 space, and a wider triangular sujDeroccipital tract of cartilage; they have risen over 

 their own roof, and up the inside of the "' epiotic " region, partly walling in the 

 posterior canal [jxs.c). 



The prootics (pr.o.) are now typical, they enclose the great foramen ovale (V.) for its 

 outer half below, and run round the front from tlience, above ; further out they have 

 climbed up on to the auditory capsule, flanking the anterior canal on its outside, and 

 covering the ampulla of the horizontal canal (a.s.c, h.s.c). 



A pair of " sphenethmoidal " centres have appeared in the chondrocranium under 

 the superorbital cave, and behind the ethmo-palatine bar (e.pa.) ; these are the 

 symmetrical rudiments of the "girdle-bone;" they are " ecto-ethmoids" now, and are 

 the proper side-wall bones protecting their own nerves (the 1st), just like the prootics 

 of the Frog, the alisplienoids of Teleostei and higher types, the orbito-sphenoids of 

 many types, and the ex-occipitals here and everywhei'e. They are separated by a tract 

 equal to their own Avidth below.* 



* Tliero is miicli variety in the formation of the girdle-hone, but these are its most essential parts; it 

 may have, however, a median element below (as in Pseitdophryne BiJu-oiin), or an azygous plate above 

 (Bfirwi temporaria, liappia (Hyperolins) hicolor). In Dactijldlira (" Batracliian Skull," Part 2, Plate 59, 

 fig. 1, s.eth.) this is a largo "Y-shapcd bone, it is free from the cartilage below it, which is not ossified so 

 far forwards. 



