198 PROF. W. K. PAEKEE ON THE MOEPHOLOGY 



Although nearly ripe for metamorphosis, there is but little promise in this stage of the 

 strange things that will appear in a few weeks afterwards. 



The Skull of an adult Spelerpes rubra, 4| inches long. 



This skull, all things considered, is one of the most remarkable I have seen; in 

 passing from the larval state to the adult, we seem to have climbed halfway up the 

 vertebrate scale. In its completeness, now that all the new things have been added, 

 it has become a singular commixture of the lower ichthyic, and the higher reptilian, 

 styles of cranial architecture. 



In making this building grow, Nature has brought out of her treasures, and fitly 

 framed together, things new and old ; thus, well observed, this skull may teach us 

 much of what is possible in the morphological stages of a vertebrate cranium. 



Having gone so far, if the Life-power of the individual had sufficed, such a skull, one 

 could imagine, might have gone on changing : a few steps in one direction would have 

 made it like that of the Emu, at the base of the Bird scries ; or in another, that of a 

 Monotrcmc, at the base of the Mammalian group. 



The large pedunculated occipital condyles (PI. XXI. figs. 2, 3, oc.c) are wide apart, 

 and the posterior basicranial euiargination is perfectly filled by the curious intercalary 

 odontoid vertebra (ocl.v), which, being ankylosed to the next («'), gives the larger joint 

 an almost exact resemblance to the second (" odontoid " or " axis ") vertebra of an Ox. 

 Yet we have just seen that this bigger vertebra is the atlas to this skull, and that the 

 " odontoid process " is in reality a small postcranial vertebra, without an arch, and 

 segmented from the hind margin of the parachordal tract. 



There is a considerable tract of cartilage, both above and below, in the occiput (figs. 1, 2) ; 

 for the rest, the occipito-otic mass, right and left, is continuous solid bone ; yet this 

 bony tract stops at the foramen ovale (5) ; for the ossification of the endocranium is not 

 intense in this type. 



The auditory masses are very large and rugged ; the huge posterior canals di.sc), as 

 they turn outwards and backwards, have a sulcus separating them from the sharp edge 

 of the exoccipital, where it forms on each side a rim to the foramen magnum. 



A very large triangular space exists between the emarginate occipital roof and the 

 front, almost transverse, margin of the " atlantal " vertebra. 



Most of the anterior canal (a. so) is tiled over by the parietals (fig. 1, p) ; but the bony 

 matter projects from beneath the notched edge of those plates, forming a crest for the 

 origin of the fibres of the temporal muscle. 



As the anterior canal is roughly covered by the parietal bone, so is the horizontal 

 (h.sc) by the supratemporal part of the squamosal (sq), which ploughs itself into the 

 substance of the prootic, raising it beyond its upper edge into a rough semicircular 

 ridge. 



Mesiad of this ridge, the prootic is scooped for the temporal muscle ; thus there is a 

 crescentic fossa, with its convex margin outside ; it reaches to the large oblique balk 

 formed by the posterior canal. 



