1897.] SKELETON OP PELODYTBS PUKCTATUS. 587 



criticism oF Parker's paper contained iu the footnote which he 

 appends. The mode ot development of the thyrohyals of Pelodytes 

 by the formation of tliyroid foramina and their subsequent 

 disruption is calculated to shake one's faith in the recognition in 

 the thyroh^'als of Anura of late and rapidly developing fifth 

 ceratobranchials as suggested by Meckel (8. p. 240) and Cuvier 

 (3. p. 397); and, although the arguments which I have previously 

 adduced in favour of this view (16. p. 112) still hold good, I must 

 confess to entertaining a suspicion that, after all, these bones 

 belong to the hypobranchial rather than to the ceratobrauchial 

 part of the visceral skeleton. 



The mandible no longer exhibits the sharp angulation of its 

 earlier stages. It is considerably longer than before, but the four 

 constituents can still be clearly recoguized. The membrane on the 

 internal or mesial surface of the ramus is much thickened, and it 

 is this which, when ossified, becomes the angulosplenial bone. 

 There is as yet no trace of a dentary. 



Stage 4. Distance from smut to root of tail, 20 mm. Length of 

 tail, 23 mm. Lenr/th of hind limb, extended, 28 mm. Length of 

 fore limb, extended, 12 mm. (Plate XXXV. fig. 4.) 



The whole aspect of the hyobranchial skeleton is beginnino- to 

 change. The ceratohyals are now massive cartilages at their 

 maximum of development, and they slope more posteriorly than 

 before. The hyoglossal notch is both broader and deeper than in 

 Stage 3. The triangular space on either side of the basihyal has 

 now become tilled up, not by encroachment of the surrounding 

 cartilages, but by the differentiation of new cartilage : the outlines 

 of the three cartilages bounding the former space are still very 

 clearly marked. There are unmistakable signs that the branchial 

 skeleton is past its prime. The arches exhibit a condition of 

 incipient collapse, but are not very much smaller than in the 

 preceding stage. The spicula have almost disappeared. There is 

 a stump remaining of that of the second ceratobranchial, and the 

 developing thyrohyal is still tipped with a remuant of that 

 cartilage which probably represents the fourth spicule, but the 

 first and third spicules have been completely absorbed. The 

 thyroid foramen (if., fig. 4) is now a distinct perforation of the 

 cartilage, and the thyrohyal is beginning to assume shape. 



Lying at the bottom of the laryngeal sinus, between the two 

 thyrohyals, is a tract of soft cartilage of crescentic form which 

 only in this stage acquires a definite outline. The sinus in which 

 it lies has been increasing in size from the very first stage, and, as 

 will be seen by referring to the figures 5-8, continues on the 

 increase. In the first three stages the loose cartilage occupies a 

 larger proportion of the space, but the tissue is of such an ill- 

 detined character that it is a matter of personal opinion wherher 

 to regard it as cartilage at all ; and, on account of its undiffer- 

 entiated nature, it is impossible to recognize its posterior limit. It 

 is therefore omitted in the first three figures. The cartilage is in 



