DEVELOPMENT OF THE SKULL IN THE BATRACHIA. 7;j 



stout angular styloid process, on the upper sui'face of" which there is a large, oval, 

 convex condyle, which rolls in the shallow cup of the suspeusorium. 



The sinuosities of the hyoid bnr are filled in by the convexities of the branchial 

 apparatus. In the middle, behind the soft basi-hyal, there is a large pyriform basi- 

 branchial (Plate 10, fig. G, h.hr.), composed of hyaline cartilage ; a short process on the 

 postei-o-inferior svu-face of this is the rudiment of a second basi-branchial segment. 



Outside and behind this median piece there is a pair of flat lozenge-shaped cartilages, 

 the hypo-branchials [h.hr.) ; these grow outwards and are connected with cartilages 

 above (inside) and below (outside) ; these latter are the branchial pouches. 



Two of the small upper cartilages are distinct from the hypo-branchials, Ijut are 

 partly confluent with the large outer bars {c.hr^., c.hr^., ex.hr.) ; the two hinder rudi- 

 ments [c.br^' ^.) are continuous with the hypo-branchial plate, and the space between 

 the tw^o is filled in with cartilage. 



The first and fourth outer bars (ex.hr^., ex.hr^.) are pouch-like, the others are thin 

 broad bands. 



Tlie rudimentary inner arches {c.h",:) are less differentiated than in tlie larva of 

 the species o? Rami and of other kinds {Cyclorhamphus, Calyptocephalus, Cystignathua, 

 &c.) that I have worked out. 



These parts are at their fullest development at this stage. 



I have already mentioned the roof-bones in relation to the fo'ntanelle ; the para- 

 sphenoid is a dagger with a guard, but without a handle. 



It seems small, yet it occupies the same place, and has precisely the same relations 

 as in the adult (Plate 2, fig. 2 ; and Plate 10, fig. 2, jxf.s.) ; it is one-third longer 

 than in the old male. Even now it is split in front : a character which is retained 

 throughout life. 



17 (continued). — (B) Second Tadpole of PseiiJi.s jmrndoxa. — 7 inches long; tail, 

 4f inches ; greatest width of tail, 2 inches ; hind legs, 3 inclies long ; fore l§gs 

 liidden. 



In this stage the legs are six times as long as in the last, and the tail two-thirds the 

 length and half the width ; here the chondrocranium is but little more than half as broad 

 across the suspensoria and only two-thirds the length." 



There are many things to be noticed in this stage besides its lessened size and more 

 oblong general shape. 



And first, the Selachian character of a huge notochord enclosed in a tubular azygous 

 cartUage is now as diflicult to find as in most Tadpoles; it has become part of the basal 

 plate by coalescence with the " parachordals" and trabeculae, and the gelatinous axis is 



• If I had oniy found these discrepancies in size in two or three, I should have thought it accidental ; 

 but my specimens are too numerous, and run over too many stages, for there to be any mistake : the skull 

 in the third stage (C) is but little more than one-third the length of that of the youngest (A). 



MDCCCLXXXI. L 



