and Systematic Position of Cheirolepis. 243 
with the clavicle. This bone is seen in Pander’s tab. viii. 
fig. 2 and tab. ix. figs. 8 & 5, but also marked 46, the same 
as the preceding *. Articulated with its lower extremity is 
the clavicle (figs. 2 & 3, cl), a bone so strong that it is con- 
spicuous in every nodule specimen, and seems to have been 
able to resist compression in very many cases where every 
thing else is crushed quite flat. This clavicle is composed of 
two parts, set at a considerable angle to each other. Of these, 
the upper or vertical part, set on the side of the shoulder and 
forming part of the hinder margin of the branchial opening, 
is of a somewhat lanceolate shape, with the posterior margin 
more convex than the anterior, and with the apex directed 
obliquely upwards and backwards to the lower end of the 
bone last described. A nearly vertical line divides the outer 
surface of this part into two, the anterior of which looks rather 
forwards into the branchial cavity. The lower part of the 
bone, much smaller and somewhat quadrate in form, projects 
inwards towards the ventral middle line; between the two 
parts, behind, is a notch from which the pectoral fin issued. 
This bone, the clavicle, is numbered 48 in Pander’s figures ; 
but in tab. ix. figs. 3 & 5 the number is placed on the element 
next to be described, which is not represented as distinct ; 
and in tab. vii. fig. 2 it is also placed on a bone which is un- 
doubtedly the operculum. The last element of the shoulder- 
girdle articulated to the front of the lower end of the clavicle 
is the dnterclavicular plate (figs. 2 & 3, 7.cl), a bone which 
among recent Ganoids is not found in Lepidosteus or Amia, 
though it occurs both in Polypterus and Acipenser and also in 
Polyodon, and in them lies, as it does here, on the so-called 
“isthmus.” It consists of a pointed plate of bone, sharply 
bent on itself along a line continued forwards from the lne 
of junction of the two portions of the clavicle, when the two 
bones are in apposition. It thus comes also to present two 
portions or aspects—the one locking upwards and outwards, 
forming part of the gill-slit below the branchiostegal rays, 
and the other covering the ventral surface of the isthmus. 
Seen from below, the ventral portion of the interclavicular 
plate is of a somewhat elongated triangular form, the apex 
directed forwards towards the symphysis of the jaw, the short 
posterior side articulating with the lower end of the clavicle, 
and in close apposition to its fellow of the opposite side, by 
about two thirds of its long internal margin, in specimens 
* There is probably an error in the lettering here, as the number 47, 
which Pander assigns to the “scapula,” does not occur on the plate 
at all. 
