41G 
MR. W. K. PARKER ON THE SKELETON 
Gl,) that spike (pr.pa.) is free, and thus, from the first, has the directly forward 
position of its counterpart in the Marsipobranchs. Moreover, in the young of Lepi- 
dosteus (Phil. Trans., 1882, Part II., Plates 30-38, p-py-) we have a prepalatine 
quite like that of the Myxinoids, and in this case it is the fore-end of the subocular 
bar which is primarily continuous with the basis cranii, but afterwards free, whereas 
it is the hind part in the embryo of the Lamprey (Plate 25, fig. 7, pd., pg ., tr.)* 
If we thus determinef that the Lamprey has a subocular arch like that of a trans¬ 
forming Tadpole, ramus the quadrate region and condyle, we have still the question 
as to whether the distal ( cornual) part of the first arch has any existence. 
In the first place, it is to me a great satisfaction to find Professor Huxley (op. cit., 
p. 421) saying of the “annular cartilage” that—“although its halves are united 
dorsally ” [it] “would seem to be essentially a post-oral structure;” it certainly is, 
if it be homologous with the divided imperfect “annulus” of the Tadpole. 
Now, there is a T-shaped median cartilage, whose transverse part lies directly 
behind the great labial ring (Plate 10, fig. 6; and Plate 18, figs. 1, 2). After 
determining (to my heart’s content) the nature of the “ styliform,” “ cornual,” and 
lingual cartilages, as the hyoid arch, lateral and basal, Professor Huxley asks—“ What 
is the median ventral cartilage which Muller regarded as the body of the hyoid ? 
The hyoidean arch is complete without it, and has no special connexion with it, the 
bent up anterior end of the lingual cartilage simply playing over it. I conceive it to 
be a median ventral element of the mandibular arch, notwithstanding that, in the 
higher Vertebrates, such an element, though the analogy of the other arches would 
lead us to expect its presence, is not known to occur. The third division of the 
trigeminal nerve passes over the expanded anterior end of this cartilage, traverses the 
ventral half of the annular cartilage, and runs along the anterior edge of the latter to 
its dorsal extremity” (p. 421). But if we look again at these cartilages in the trans¬ 
forming young of the great Lamprey (Plate 10, fig. 6), we shall see that the paired 
styloid cartilages of the lower lip are attached by their broader inner ends to the 
annular cartilage and are curved at their free and outer ends, so as to resemble very 
closely the form and relations of the small mandibles of the Tadpole (see my 3rd Paper 
“ On the Skull of the Batrachia,” Plates 2, 3, 4, 11, 15, 17, 22, 30, and 38). 
Now, it occurred to me some time ago that these were the true Meckelian rods, but 
the late Professor Balfour assured me that I had no proof sufficient to sustain this 
view. 
Then as to the median T-shaped cartilage ; such a thing as a median mandibular 
element, well formed, but not segmented off from the Meckelian rods, does exist in 
“the higher Vertebrates.” I have already shown it in the Green Turtle and the 
* The pharyngo-hyal element or liyomandibular is developed continuously with the skull in Lpppidosteus, 
thus throwing light on the second arch of the Myxinoids. 
t The difficulty with regard to the relation of the branches of the trigeminal nerve to the sub¬ 
ocular bar and fenestra has been dealt with in the First Part (pp. 401-403). 
