566 MR. J. B. SUTTON ON THE CRANIAL ARCADE. [Dec. 2, 



2. Observations on the Parasphenoid, the Vomer, and the 

 Palato-pterygoid Arcade. By J. Bland Sutton, 

 F.R.C.S., Lecturer on Comparative Anatomy at the 

 Middlesex Hospital Medical College. 



[Received November 10, 1884.] 

 (Plates LIII. & LIV.) 



In the well-known ' Lectures on the Elements of Comparative 

 Anatomy/ 1864, Professor Huxley, in describing the structure of 

 the Pike's skull, draws especial attention to a bone forming part of 

 that fish's cranio-facial axis, which up to the time of the delivery of 

 those admirable lectures had been denominated basi-sphenoid. 



Concerning this bone the Professor states : — " It differs from any 

 of the ossifications of the basi-sphenoidal cartilage in Man, not only 

 by extending backwards beneath the basi-occipital, but by stretching 

 forwards beneath the pre-sphenoidal and ethmoidal cartilages to 

 within a short distance of the anterior extremity of the cranium ; 

 and in the still more important circumstance that it is an ossification 

 within the perichondrium, which can be stripped off, in skulls which 

 have been macerated, or steeped for a short time in boiling water, 

 without injury to the cartilage upon which it is developed. 



" Mr. Parker has shown, in his valuable paper on Balceniceps 1 , that 

 the so-called basi-sphenoid of birds is developed from three ossifi- 

 cations — a central one, the true basi-sphenoid, and two lateral and 

 inferior centres, the ' basi-temporals ' (Parker), which appear to 

 correspond with the lingulce of Man. The thought readily arises 

 that the single bone x (Plate LIII. fig. 1) may correspond with 

 these two basi-temporal ossifications. The latter, however, appear 

 to be cartilage ossifications like the lingulce themselves ; and upon 

 the whole I think it will be safer, at any rate for the present, to 

 regard the bone x as peculiar to the branchiate Vertebrata and to 

 confer upon it the special name of ( parasphenoid ' " (p. 170). 



For twenty full years has the name parasphenoid found a place in 

 anatomical nomenclature, and as such it will probably continue to do 

 so, but that it is a bone peculiar to branchiate Vertebrata is an 

 opinion unsupported by facts and altogether untenable. It is one of 

 the objects of this paper to show that its representative in the skulls 

 of Mammalia is the bone known as the " vomer." 



It must of course seem presumption on my part to differ from 

 Prof. Huxley on a subject to which he has devoted his critical mind 

 for so many years ; nevertheless, I ask for unbiassed attention, as for 

 some years past the question has occupied my best thought and labour. 



Stated briefly, the relations of the parasphenoid amount to these 

 in the Pike's skull : — 



It is a bone of membranous origin, having the shape and general 

 appearance shown iu Plate LIII. fig. 2. By its upper surface it is 

 in relation with the under surface of the basi-occipital bone, the 

 1 Trans. Zool. Soc. vol. iv. 



