DEVELOPMENT OF THE SKULL IN THE BATRACHLA.. 133 



the quadrate (7.) — the latter is partly ossified near the trochlea or condyle (q-c.) 

 by the quadrato-jugal (q-j.). 



The Eustachian openings (eu.) are large, reniforni, and transverse ; the annulus {(i.ty.) 

 is large and its horns are confluent, above. 



The stapes (fig. 5, st.) is large, truncate in front, and has a large knob for muscular 

 attachment. 



The inter-stapedial [i.st.) is well developed as a "sesamoid" cartilage; the medio- 

 stapedial (in.st.) is I'oughly pistol-shaped ; the extra-stapedial [e.st.) is a large spatula, 

 giving off a ligulate supra-stapedial (s.st.), which is confluent, above. 



The mandible (fig. 3) is normal, but the dentary [d.) is much longer than usual, 

 and the articular portion has an endosteal " articulare " (ar^.) as in Bomhinator. 



The basi hyo-branchial plate (fig. 4) has the notch very deep ; the cerato-hyals 

 (cht/.) expand to twice their upper size, in the middle, and have a small hypo-hyal 

 lobe ; they are free above. The lateral lobes, fore and hmder, are well developed, 

 but the thyro-hyals {t.hy.) are near together in front, and are short; they have a 

 pedate unossified free end, and each has, on its outside, a small oblong nucleus of 

 cartilage sticking to the bony shaft.'" 



Here again we see, as in Pelodytes, the V-shaped perichrondrial bone, with its angle 

 backwards, lying on the under face of the basal plate near the thyro-hyal ; it is an 

 attempt to form a basi-brancliial bone. 



The investing bones correspond very closely with those seen in the skulls of 

 Pelodytes and Bomhinator, and they are also very similar to those of the more 

 delicate Australian Hylce. The fronto-parietals {f.})-) are tlfin laths of bone, lying 

 on the skull- wall, and cm-ved so as to bind round the two fontanelles and the front 

 of the ear-capsule, just at its inner edge. But they fail to cover the superoccipital 

 region, and only partly hide the girdle-bone. 



The nasals (n.) have the usual form, and in theu' fullness of size and shape cover 

 in the imperfect nasal roof. 



The pi'emaxillai'ies (px.) are extended widely ; the maxillaries, quadi'ato-jugals, and 

 squamosals {mx., q.j., sq.) are normal but feeble ; the quadrate is partly ossified by the 

 second of these ; the third only binds on the edge of the tegmen tympani. 



The parasphenoid (fig. 2, pa.s.) is large in its fore part, but its wings are narrow 

 externally, and the hind part is but little produced. The vomers (v.) are very large, 

 but in this wide-muzzled Frog they only reach the septum nasi inwardly, and outwardly 

 do not touch the maxillaries. The dentigerous part is oval and transversely placed ; 

 the interspaces between these tracts is almost equal to the tracts themselves. There 

 are no septo-maxillaries. 



It is impossible to compare this skull with that of Bomhinator and Pelodytes without 

 seeing that these three have many things in common, and that in so fax as they agree 



* Mr. Howes has sbown me, in his exquisite dissections of the Stnrgeon at the South Kensington 

 Museum, that the visceral arches of that fish have many small nuclei of cartilage inside the periosteum. 



