504 PROF. RAY LANKESTER ON THE HEARTS OF 
when traced into the ventricular cavity is found to form a considerable lobe there (A in 
figs. 14 and 15). ‘This possibly is the representative of the great basilar fibro-cartilage 
of Dipnoi, whilst the third pad is relatively small, and might be expected to disappear 
were the larger one (A) to encroach upon it. 
I do not attach any importance to these hypothetical identifications as showing affi- 
nities between Chimera and the Dipnoi, but rather I must insist on the fact that there 
is so little community of structure. 
The auricle of Chimera is not sacculated like that of Protopterus, but has a very 
distinct pinched-off sinus (fig. 15) which opens into the auricle by a limited slit-like 
orifice protected by valvular folds (Sav). 
It is of some interest in connexion with the development of an auricular septum in 
this and in that animal to notice that in Chimera the auricle is incompletely divided 
by a septal ridge into two compartments, into one of which the sinus opens, whilst 
from the other leads the small tricuspid auriculo-ventricular passage. 
DESCRIPTION OF THE PLATES. 
PLATE LXXXIII. 
Fig. 1. Heart of Ceratodus Forsteri, right lateral view, natural size: BA, branchial 
arteries; Per, remnant of pericardium; AC, arterial cone; Aw, auricle; 
Vn, ventricle. 
Fig. 2. Heart of Ceratodus: the ventricle and upper limb of the arterial cone have 
been opened and the cut edges pinned back: Sp v, spiral valve; FC, basal 
fibro-cartilage ; other letters as in fig. 1. 
Fig. 3. The same heart further dissected, the lower limb of the conus being now 
opened by a cut indicated by the dotted line in fig. 2. AVV, auriculo-ven- 
tricular curtain valve; wv, situation of the small pocket valves; other letters 
as in figs. 1 & 2. 
Fig. 4. The same heart further dissected by a cut passing along the dotted line marked 
in fig. 3. Lv, liver; VC, vena cava; other letters as in preceding figures. 
Fig. 5. Inner wall of lower limb of arterial cone spread out flat, and enlarged so as to 
show the undescribed pocket valves. Sp. V, spiral valve. 
Fig. 6. A single valve from fig. 5, enlarged so as to show the chorde tendinee. 
Fig. 7. Diagrams of the arterial cone and its longitudinal spiral valve. A, the cone 
itself; the upper and transverse limbs have their anterior walls removed. 
The dotted line, ss’, indicates the line of origin of the longitudinal ridge or 
“spiral” valve. B, spiral valve of Protopterus; the shaded border (ss') is 
that which is attached to the wall of the conus. C, the shorter spiral valve 
of Ceratodus; ss', attached border. 
