SKULL OF PTERANODON INGENS Marsh. 11 



being only 3 mm . To give a better conception of the complete skull, a composite 

 restoration, based upon the type and No. 2473 jointly, is shown in Plate IV, figure 1. 



Since the great supraoccipital crest is one of the most striking characters of the 

 genus, it is of the highest importance to learn what its true function may have been. 

 Professor Seeley in " Dragons of the Air," p. 70. has aptly compared the Pteranodon 

 crest with those borne by the Cormorant and the Chamaeleon, stating by way of ex- 

 planation that the separate and movable crest of the Cormorant (Phalacrocorax) is not 

 strictly the equivalent of the fixed crest of the pterodactyl. Although the Pteranodon 

 crest is now known to have been much longer than it was supposed to be when first 

 described, the recent animals referred to by Professor Seeley help greatly toward a 

 satisfactory understanding of its function, especially when they are considered as stages 

 in a developmental series including Plotus (the Darter), Phalacrocorax, Chamaeleo, and 

 Chelydra. A brief review of the comparative anatomy of these types of vertebrate 

 crania may throw light upon the present discussion. 



In Chelydra serpentina, the Snapping Tortoise (Y. U. Osteol. Coll., No. 5454), the 

 united supraoccipital and parietals form a strong crest of considerable length (Plate V, 

 figure 10). Dissection of the head shows that the main function of this crest is to furnish 

 the origin of the divisions of the enormous musculus temporalis, which gives this tor- 

 toise its dreaded power to seize and lacerate its prey. Another noteworthy reptilian 

 example of this structure is offered by the Chamaeleon. Plate V, figure 11, of Chamceleo 

 vulgaris, shows the remarkable extension of the parietals and supraoccipital, strengthened 

 on each side by the elongated squamosals. The definition of the temporalis muscle 

 given by Mivart {On the Myology of Chamaeleon parsonii, Proc. Zool. Soc. London, p. 850, 

 1870), is quoted here : — 



" Temporalis. This muscle is of prodigious size ; and it would be interesting to know 

 what is the use to the Chameleon of so singularly voluminous a temporal. It springs 

 from the whole surface of the temporal fossa, and from the occipital crest, where it 

 appears on the back of the head, having the most anterior part of the longissimus 

 dorsi on its inner side, and the complexus on its outer side. It is inserted into the 

 upper border of the mandible, between the coronoid process and the articular surface." 



Since the origin of the temporalis extends so widely over the lateral surface of the 

 Chamaeleon's crest, the inference may be drawn that the principal direct function of the 

 crest is to serve for the attachment of this remarkably powerful muscle. The fact that 

 the animal's feeding habits, as far as known, do not require any such development of 

 the muscles for closing the jaws in no way invalidates this conclusion. As in Chelydra 

 so here in Chamaeleo, the insertions of the longissimus dorsi and of the complexus 

 are situated so low down on the occipital arch that the crest is not to be considered 

 as a lever to facilitate the elevation of the head. This is equally true of the insertions 

 of the neck muscles in the genera of recent birds to which reference is now made. 



The occipital styles seen in two genera of Totipalmate birds, Phalacrocorax and 

 Plotus, have been the cause of considerable difference of opinion among zootomists, 

 and many thrusts have been given and parried on the subject of the " xiphoid bone " 

 so aptly named by an early writer, William Yarrell, Esq., F. L. S., etc., whose instructive 

 paper: "On the use of the xiphoid bone and its muscles in the Corvorant" (Sowerby's 

 Zool. Jour., vol. iv, 1828) contains two excellent engravings of the skull of Phalacro- 

 corax carlo. Owing to the difficulty of reproducing these engravings, figures (Plate V, 

 figures 13 and 14) have been made from a skull of P. dilophus (Y. U. Osteol. Coll., 



