584 MR. J. B. SUTTON ON THE DEVELOPMENT [JuUC 2, 



but the basisphenoid and its associated nuclei are in no small degree 

 interesting. 



Mr. Parker, in his very valuable paper, " On the Skull of the Com- 

 mon Fowl" (Phil. Trans. 1869), introduces us to two very remark- 

 able bones which he names the basitemporals. I will describe them 

 in Mr. Parker's own words : — " The subcranial region, which in the 

 Frog is ossified by the basitemporal wings of the parasphenoid, is 

 here supplied witli a pair of distinct and large basitemporal bones 

 which extend from near the median line, beneath the cochlea and 

 so far outwards as to constitute a floor for the tympanic cavity ; their 

 anterior limit is near the fore margin of the alisphenoid cartilage. 

 These ossifications arise in a thick weft of fil)rous tissue in the hinder 

 part of the palate ; the matrix is abundant in the middle line, extend- 

 ing forwards to the bone next to be described. The Eustachian 

 tubes run forwards and inwards above the anterior edge of these bones, 

 and meet in the middle line beneath tlie pituitary fossa"'. The 

 Fowl's basitemporals are shown on Plate XXXV. fig. 1. 



It is needful to explain what is here meant by the basitemporal 

 ■wings of the parasphenoid. 



Underlying the Frog's skull (as shown in Plate XXXV. fig. 2) is a 

 dagger-shaped bone termed by Prof. Huxley the parasphenoid, but it 

 is simply the representative of the vomer of the mammalian skull : the 

 lateral portions marked L in the figure are what Mr. Parker refers 

 to as the basitemporal portions. The morphological value which 

 the latter writer places upon the bird's basitemporal is so singular 

 that it is needful again to quote his own description, contained in a 

 footnote in the "Fowl" paper: — "From a careful comparison of 

 these parts in the lower Mammalia witli those of man, 1 feel satisfied 

 that the bony lingulte in that class answer to the basitemporal 

 rudiments of the parasphenoid" (p. 770). This comparison was 

 first suggested to Mr. Parker by Prof. Huxley, who states in a foot- 

 note in one of his admirable 'Lectures' that " Mr. Parker agrees 

 with my suggestion that the basitemporals of the Sauvopsida are the 

 homologues of the linguleB sphenoidules of Man" (p. 220). 



My intention is now to proceed to show beyond all doubt that the 

 "suggestion" and the " agreement" are out of harmony with the 

 facts of the case and opposed to the usual methods of morpliological 

 reasoning. 



The lingulse of the Mammalian sphenoid have no relationship 

 whatever with the basitemporals of birds. 



The proof is as follows : — The basitemporals, and no one doubts 

 the facts, arise in membrane. It is a well-establisheil truth that a 

 bone preformed in cartilage cannot be homologous with one simply 

 of membranous origin. The basitemporals are membrane-bones ; 

 the lingulsB are preceded by cartilage. On this ground alone the 

 evidence of identity fails. On Plate XXXV. fig. 3, is represented the 

 base of the skull of a young Ostrich (Strut /no camelus) : two distinct 

 osseous nuclei are seen lying on either side of the basisphenoid, 

 between it and the alisphenoid ; they are developed in cartilage, thus 

 in mode of ossification as in their relations they correspond to the 

 ' Morphology of the Skull, p. 2.31. 



