f)8 PROF. G. B HOWES AND MR. H. H. SWINNERTON ON THE 



12. That the epipterygoid bone is the product of ossification of the ascending process 

 of the pterygo-quadrate cartilage, and that the special feature of the quadrate bone is 

 an extension of its ossific head into the latter for approximation to the epipterygoid. 



13. That the columella auris and stapedial processes are alike direct derivatives of 

 the hyoid arch, with which they are continuous at all stages, and that structural 

 complication is due to overgrowth of the same. 



14. That the upper end of the hyoid cornu is attached to the quadrate only, and 

 that there is a fleeting "jointing " of the former throughout its course. 



15. That in the meeting of the pterygoids and vomers, the latter play a part leading 

 up to the conditions occurring in the Chelonia and Plesiosauria. 



16. The cartilaginous pterygo-quadrate is in its detailed characters most nearly 

 comparable to that of the Apodal Batrachian Ichthyophis. 



17. That each of the three segments of each of the "abdominal ribs'' (gastralia) 

 arises by union of a number of calcifications, and that the median segment may be paired. 

 That the "plastron " is present in a degenerating form. 



18. That in their early differentiation the membrane-bones of the head and face are 

 predominantly circumorbital in position. 



19. That there is no supratemporal bone recognizable at any stage as a distinct 

 element. 



20. That the hip-girdle in its development is of a lower type than the Lacertilian, 

 and that there are two types of pelvis present in adults. 



21. That the fifth tarsale has no existence in ontogeny, and that the basal element 

 of the fifth digit of the hind limb is a metatarsal. 



22. That there are apparently three centralia carpi represented during development, 

 and that a centrale is incorporated in the " astragalus." 



23. That calcified vomerine teeth are not present during encapsulation within the 

 egg-shell. 



24. That of the three pairs of upper incisors, the middle certainly disappear 

 and the inner may become tricuspid. 



25. That the cheek-teeth appear to consist of two series an early developed 

 alternating set, and a later posterior and structurally uniform set. 



16. That there arise within the occipital region and the individual vertebral segments 

 sustentacular ligaments, for support of the medulla and spinal cord. 



Conclusions. Paragraphs 16, 17, 20, and 22 of our Summary add fresh testimony to 

 the belief in the Batrachian affinities of the living Sphenodon, while paragraph 15 

 strengthens the demonstration of its Chelonian resemblances and extends these to the 

 Plesiosauria. Paragraph 17 proves the creature to be a highly modified representative 

 of its Suborder, but at the same time to pass through a developmental phase realistic 

 of the lower Suborder of the Khynchocephalia, as now classified ; and the same is 

 true of paragraph 24, by comparison with the Proterosauria (especially Palaeohatteria). 

 Of the supposed Agamid affinities we have written enough (antea, pp. 4, 22, 46). 



