216 MR. R. OWEN ON THE STRUCTURE OF THE HEART 
the branchial divisions of the vena cava in the Cephalopods, which also in that class are 
contained within a large pericardium, and serve, besides other uses, as reservoirs of 
blood to the branchial ventricles. 
The auricles are placed on the dorsal aspect of the ventricle, and more to the left 
than to the right side: they are not, however, so absolutely to the left side as Meckel 
describes ', but, when fully distended, advance forwards, as in Pipa, on both sides the 
ventricle and bulbus arteriosus, so as almost to encompass and conceal those parts. The 
size of the combined auricles is thus very considerable in proportion to that of the ven- 
tricle. In Amphiuma and Menopoma the auricles are proportionately smaller, and situated 
more completely to the left of the ventricle. The margin of the auricle in Amphiuma is 
but slightly notched as compared with that of the Siren ; in Menopoma it is almost entire. 
The ventricle in Str. lacertina is of an oblong-oval and slightly flattened form, similar 
to that of Ophidia: a slight notch or tendency to a division is observable at the apez, 
which lodges a branch of the coronary vein”, which is continued from this end of the 
ventricle into the inferior cava. The opposite end of the ventricle projects a little be- 
yond the origin of the artery. The serous investment of the ventricle, besides being 
continued along the bulbus arteriosus to the anterior end of the pericardium, is reflected 
also from the lower third of the dorsal margin of the ventricle upon the venous sinus ; 
and between these two layers the coronary vein is continued to the inferior cava, as in 
the Crocodile and some Chelonia. 
The parietes of the ventricle (which measured -,ths of an inch in length and -:,ths 
of an inch in breadth,) are about =2,th of an inch in thickness, and of a loose fasciculate 
structure. The most interesting appearance within the cavity is a rudimentary septum ® 
extending from the apex half way towards the base of the ventricle, and terminating in 
a concave edge directed towards the orifice of the artery. The whole inner surface is 
reticulated by the decussating carnee columne. 
The valvular structure at the orifices of the auricles was not very conspicuous in the 
specimen examined. A slight membranous production extended from either side the 
bar or septum which separated the orifices, and this septum was attached by a fleshy 
column to the parietes of the ventricle. 
The artery comes off about a line above the auriculo-ventricular apertures. It makes 
a half spiral curve, and then dilates into an elongated muscular bulb, which extends 
straight forwards to the anterior end of the pericardium, and there emerging, divides at 
once into the six branchial arteries, three on each side. There are two valves, one large 
and one small, at the origin of the artery ; but the latter is a mere ridge. At the com- 
mencement of the bulb there are two similar but smaller valves. The bulb itself is 
almost wholly occupied by a cylindrical fleshy valvular body, attached posteriorly, and 
marked anteriorly with grooves which lead to the several arteries given off above: the 
form of the canal, as seen on a transverse section, is, at this part, crescentic. 
' Loe. cit., p. 216. 2n, Fig. 2. 3 f’. Fig. 3. 
