39] THE SKULL OF AMIURUS— KINDRED 39 



sphenoid. In the piscine nomenclature commonly used at the present time, 

 this ossification is regarded as the basisphenoid, although it has been known 

 for a long time that it is not the homologue of the basisphenoid center of ossifi- 

 cation of man, from which the terminology is derived. In all fishes where it 

 appears as a distinct bone, it lies anterior to the hypophysis and is developed 

 from connective tissue membrane. Cuvier called it the 'sphenoide anterieur, ' 

 but Kallmann (1837) pointed out that Cuvier's diagnosis of this bone as the 

 homologue of the presphenoid region of man was incorrect. Concerning this 

 bone, Kallmann says: ''Ein vorderer Keilbeinkorper ware wie bei die Sauge- 

 thieren und wie als der Name sagt, vor dem hintern zu suchen. Aber mit 

 Cuvier (der die Knochen Fig. 24 g und Fig. 25 u. 26 beide vordern Keilbein- 

 korper nennt) einen auf den vordern Theil des Keilbeins oder auf die Mitte 

 desselben sich herabsenkenden Knochen Keilbeinkorper nennen, heisse aller 

 Analogic. " 



Reasoning upon this basis and continuing to regard the parasphenoid as 

 the homologue of the basisphenoid of the mammalian cranium, he named the 

 bone in question, the 'sphenoide superior' and maintained that it was found 

 only in fishes and that it had varying developments in these. 



Huxley (1864) studied the development of the parasphenoid in Esox and 

 concluded that it was a dermal derivative and hence not the homologue of the 

 basisphenoid ossification center of man, a purely cartilage development 

 posterior to and below the hypophysis. He named Kallmann's 'sphenoide 

 superior, ' the basisphenoid, but remarked that it was only comparable to the 

 anterior part of the basisphenoid and that the rest of the element persisted 

 as cartilage. His reasons for regarding this bone as the homologue of the 

 basisphenoid are, that in the foetal human skull the basisphenoid contributes 

 nothing toward the posterior boundary of the pituitary fossa, which is formed 

 by the long cartilaginous synchondrosis which connects the rudimentary basi- 

 sphenoid with the basioccipital. Thus he regarded the bone as a rudimentary 

 basisphenoid. Owen, following St. Kilaire, called it the entosphenal, and 

 regarded the parasphenoid as divided into a presphenoid and basisphenoid 

 part, regardless of the work of Huxley. Allis (1897) regarded it as the homo- 

 logue of the presphenoid bone of man and yet called it the basisphenoid. 



The development of this bone is the keystone in making the homologies, 

 and all who have studied its development have found that it develops from 

 connective tissue membrane anterior to the hypophysis, and hence cannot be 

 the homologue of the basisphenoid bone of man — a cartilage bone developed 

 from the basis cranii. The cartilage which is enclosed within the parasphenoid 

 and this ossification in Amiurus may be the homologue of the basisphenoid 

 which never ossifies. This is an ossification peculiar to fishes and, together 

 with the parasphenoid, it becomes gradually replaced in the higher vertebrates 

 by the ossification of the basis cranii. Since it is neither the homologue of the 

 basisphenoid nor of the presphenoid, it must be regarded as a distinct bone and 



