DEVELOPMENT OF THE SKELETON OF THE TUATARA, 71 
ontogeny; the investigation of Kiikenthal, which has brought to light the remarkable 
fact | that the fourth and fifth digits of the Crocodilian fore limb are developmentally 
hyperphalangeate—all testify to the great potentiality of the digital blastema?, and do 
away with the value of the mere numerical difference as a criterion of affinity. 
The question thus resolves itself into this—are the ‘Terrestrial Vertebrata the 
descendants of the afore-defined Batrachian-Reptilia or of Reptilian-Batrachia? The 
problem for the immediate future lies in the study of the occiput, the sternal skeleton, 
and the quadrate; and, to our thinking, Sclerocephalus, with its multisegmented 
and structurally simple “ plastron,” its “fanged” vomer, its elongated dentigerous 
pterygoid *, and its quadrate, points the way. 
It is certain, but most unfortunate, that in its earliest forms, the sternum, known to 
us only in its definitive conditions, was cartilaginous, and has been lost to us in the 
palzeontological record. The discovery by Osborn, however, of a cartilaginous sternum 
in the fossil state+, gives us hope. The decision must lie with the future. 
Anatomist and paleontologist must approach the question in the spirit of a combined 
morphological brotherhood ; and its solution will mark an epoch in the progress of 
the vertebrate morphology of the era of its discovery. 
Addendum, Nov. 16, 1900. 
Shortly after the proofs of this Memoir were revised for press, there reached us a recently 
published paper on the organogeny of Sphenodon, by Professor H. Schauinsland, of Bremen 
(Archv. Mikr. Anat. Ba. lvi. pp. 447-867). Although it came to hand too late for comment in 
our pages, we observe from its perusal that it is in places erroneous, and that we should have lost 
nothing by its earlier appearance, since its author is insufficiently acquainted with the literature 
of the subject, and apparently ignorant of the recent important papers by Dendy, now more than 
a year old. 
List OF THE MORE IMPORTANT MEMOIRS DEALING WITH SPHENODON. 
$38, Arsrecur, P. Note sur la présence d’un Rudiment de Proatlas sur un exemplaire de 
Hatteria punctata. Bull. Mus. Belg. tom. ii. pp. 185-193. (First record of pro-atlas.) 
83. ——. Epiphyses osseuses sur les Apophyses épineuses des Vertébres d’un Reptile 
(Hatteria punctata, Gray). Bruwelles, 1883. Pp. 1-6. 
868, Baur, G. Die zwei Centralia im Carpus von Sphenodon (Hatteria) und die Wirbel von 
Sphenodon und Gecko verticillatus, Laur. (G. verus, Gray). Zool. Anz. Bd. ix. pp. 188-190. 
1 Kiikenthal, W.: Morphol. Jahrb, Bd. xix. 1893, p. 50. 
? In a manner akin to that of the passing “jointing” of the hyoid cornu described in the text (antea, p. 48). 
> It is unfortunate that its parasphenoid is unknown, but it must assuredly have possessed one, and that 
probably dentigerous. 
4 Osborn, H. F.: op. cit. antea, p. 14. 
