68 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 distimct 
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 proyes 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 Rhynchocephalia, as now classified; and the same is 
true of paragraph 24, by comparison with the Proterosauria (especially Paleohatteria). 
Of the supposed Agamid affinities we have written enough (antea, pp. 4, 22, 46). 
