240 REPORT—1846. 
In mammals the normal completion of the hyoidean arch, as it first ap- 
pears in fishes, is again resumed, and that not by a slender cartilage, as in 
the frog, but by a chain of bones, in which we again recognise the cerato- 
(fig. 24, 40), epi- (39) and stylo- (3s) hyals suspending the basihyal (41) and 
the tongue to the base of the skull, often to the petrosal, sometimes to the 
tympanic, or to the mastoid, or to the exoccipital. The ungulates and the 
true carnivora best display this type. 
In man (fig. 25) the ceratohyals are reduced, as in birds, to mere tuber- 
cles of bone (40), and the extent of the arch between them and the stylo- 
hyals, which become anchylosed to the temporal bones, retains its primitive 
ligamentous condition. Occasionally, however, ossification extends along 
the stylohyoid ligament, and marks out, as in the specimen figured by 
Geoffroy St. Hilaire (Philosophie Anatomique, pl. 4, fig. 87), the more nor- 
mal proportions of the ceratohyal, and also the epihyal. Other examples of 
this ‘ monstrosity’ are recorded in works on anthropotomy. The thyro- 
hyal (4s)—the last remnant of the branchial arches—maintains more con- 
stancy in its existence and proportions ; but manifests its true character of 
free suspension below the skull, and an articulation by short ligaments to the 
angles or horns of the thyroid cartilage. 
The remarks already made on the special homologies of the parts of the 
scapular arch and its appendages, preclude the necessity of further extending 
the present part of this Report. 
Part II].—GeneraL Homotoey. 
On taking a retrospect of the results of the researches of anatomists into 
the special homologies of the cranial bones, the student of the science, how 
little soever practised in such inquiries, cannot but be struck with the amount 
of concordance in those results. It must surely appear a most remarkable 
circumstance to one acquainted only with the osteology of the human frame, 
that so many bones should be, by the common consent of comparative ana- 
tomists, determinable in the skull of every animal down to the lowest osseous 
fish. This fact alone, so significant of the unity of plan pervading the ver- 
tebrate structure, has afforded me, at least, a large ground of hope and 
much encouragement to perseverance in the reconsideration of those points 
on which a difference of opinion has prevailed ; and in the re-investigation of 
what is truly constant and essential in characters determinative of special 
homologies. 
In this, as in every other inquiry into nature, the first labours are neces- 
sarily more or less tentative and approximative: but if errors have to be 
eliminated in the course of successive applications of fresh minds to the 
task, truths become confirmed and established. And I regard the body of 
such truths (see Table I.) to be now so great, in respect of the determination 
of the homologous bones in the heads of all vertebrate animals, as to impe- 
ratively press upon the thinking mind the consideration of the more general 
condition upon which the existence of relations of special homology depends. 
Upon this point the anatomical world is at present divided, lacking the 
required demonstration. The majority of existing authors on comparative 
anatomy have tacitly abandoned*, or with Cuvier and M. Agassiz, have 
* Waaner, ‘ Lehrbuch der Zootomie,’ 8vo, 1843, 1844. Srezonp and Srannivs, ‘ Lehr- 
buch der Vergleichende Anatomie,’ 8vo, 1845, 1846. Mrtne-Epwarps, ‘ Elemens de 
Zoologie,’ 8vo; 1834. Prof. Rymer Jones, ‘ Outline of the Animal Kingdom and Manual 
of Comparative Anatomy,’ 8vo. 1841. The sentiments which this pleasing and instructive 
writer expresses, are probably akin to those which haye influenced the above-cited authors 
