DEVP]LOPMENT OF THE SKULL IN THE BATRACHIA. 157 



Here, again, in the large bony inter-stapedial and the suppressed supra-stapedial 

 we have a curious mixture of what is arrested and over-developed. 



The mandibles (fig. 8) are well developed and quite normal, except that the articular 

 condyle is very deeply sidcate, so as to be the exact reniform counterpart of the quad- 

 rate condyle of other types ; this is in conformity with the very deep scooping of the 

 part on which it rolls (figs. 6 and 7, q.c). 



The cerato-hyal band (fig. 8, c.hi/.) and the hypo-hyal lobe {li.hij.) are (piite normal, 

 but the large front notch, as in the other kind (fig. 3), is unusually short. 



The whole jalate is lai'ge, and here the lateral lobe is notched in front, is of large 

 extent, and is only separated from the hinder small lobe by a gentle emargination, 

 there is an approach to this in the other (fig. 3), but here (fig. 8) we have it well 

 developed, and it is a rare condition. 



The thyro-hyals (fig. 8, t.hy.) are rather large and only moderately divergent, they 

 show age in a remarkable way ; the inner edge of each is produced into a large wing 

 of periosteal hone; moreover, the basal plate (h.li.hr.) is all converted mto true hone, 

 except at its edges. 



More or less calcification often occurs and is typical ; sometimes true hone appears 

 close to the thyro-hyals ; here, however, the bony substance reaches to the front iiotch, 

 and runs far into the latei'al lobes. 



The investing bones are exactly such as we see in newly transformed Frogs of the 

 common kind. The fronto-parietals {j-p-) are quite similar to those of the young 

 Hylarana (figs. 1 and 2), and the nasals (h.) are small, crescentic shells, covering very 

 little of the cartilage. The marginal bones (px., mx., q.j., sq.) are frail splints, like the 

 palatine and pterygoid ectostoses. The parasphenoid has similar wings to the other, 

 and its main part is short but very broad ; here again we have the characters of a young 

 Frog. The vomers (fig. 7, v.) are very minute toothless crescents, and there are no 

 septo-maxillaries. 



Many of the characters of this dwarf are those of a young typical Rana, but the 

 intense ossification of certain regions show that it is an adult arrested at certain points. 

 It differs from the "norma" in the following particulars : — 



1. The cranial notochord is large and persistent. 



2. The occipito-otic centres are arrested. 



3. There Ls only one, and that a very large, fontanelle. 



4. The mid and fore skull are very wide, and the latter has the roofs veiy tumid, 

 as in young species of other kinds. 



5. There is a prenasal rostrum. 



G. The palato-suspensorial ectostoses are an-ested. 



7. The quadrate condyle is of an unusual form, being deeply scooped, and its counter- 

 part in the mandible being reniform with a very definite "hilus." 



8. The retention of the larval "orbitar process." 



0. The intense ossification of the inter- and the absence of the s»y)ra-stapedial. 



