SOME PARTS OF THE SKELETON OF . FISHES 283; 
2. On the development y the palato-pterygoid arc and hyomandibular 
suspensorium in Ltshes. 
On examining the region in which the complex mass of bones. 
comprehended under the above name eventually lies in an embryo. 
Gasterosteus, about $d of an inch long, I found in their place a 
delicate inverted cartilaginous arch attached anteriorly by a very 
slender pedicle to the angle of the “ facial cartilage” formed by the 
union of the two trabeculae cranii, and posteriorly connected by a 
much thicker crus with the anterior portion of that: part of the 
cranial wall which incloses the auditory organ. The crown of this. 
inverted arch exhibits an articular condyle for the cartilaginous. 
rudiment of the mandible. Its posterior crus is not, as it appears 
at first sight to be,a single continuous mass, but is composed of 
two perfectly distinct pieces of cartilage applied together by their 
respective anterior and posterior edges. The anterior is continuous 
below with the condyle, but ends above in a free point. The pos- 
terior is continuous with the cranial wall above, but ends below 
in a free point immediately behind the condyle. The posterior 
edge of this last portion (which I shall term the hyo-mandibular 
cartilage, as it is the means of suspension of both hyoid and man- 
dibular arcs to the skull) has, above, a rounded condyle for the 
operculum, while below this, it gives attachment to that cartilage 
which eventually becomes the styloid element of the hyoidean arc. 
That part of the cartilage which lies above the attachment of this 
element becomes, by its ossification, the “temporal” of Cuvier; that 
which lies below it gives rise to Cuvier’s “ symplectique.” 
The anterior division of the posterior crus, the condyle, and the 
anterior crus of the inverted arch I have mentioned, constitute an 
inverted V-shaped “ palato-quadrate” cartilage. The anterior part 
of the anterior crus ossifies, and becomes Cuvier’s “ palatine ;” the 
posterior. part gives rise to his “transverse” and “pterygoid ;” the 
condyloid portion, when ossified, becomes his “jugal;” and the 
extremity of the ascending process from this or the anterior division 
of the posterior crus becomes his “ tympanique.” 
The operculum, suboperculum, interoperculum, and preoperculum, 
are developed in the branchiostegal membrane apart from the other 
bones. 
These embryological facts are of great importance, as they enable 
us to understand, on the one hand, the different modifications of the 
palato-suspensorial apparatus in fishes, and on the other hand, the 
