304 MR. F. E. BEDDARD OM THE [ISToV. 3, 



the vein has a much shorter course within the pericardium, and 

 leaves that cavity at its posterior corner on each side, instead of 

 passing forward and running for some space within the pericardium 

 at an angle with its foi-mer course. Hyrtl figures veins in the 

 place of the gubernaculum which he describes as ramifying over 

 the heart ; but he describes no coronary artery. On the contrary, 

 I find a very distinct coronary artery (see jj. 308), but have seen 

 no coronary veins. Tn the interior of the ventricle I could find 

 no traces of a subdivision into two cavities. The demarcation 

 between the pylangium and the synangium is quite visible exter- 

 nally, and plainly to be seen in the accompanying drawing (text- 

 fig. 29, Tp. 303). The entire truncus arteriosus measures 43 mm. 

 as against 34 mm., which is the extreme length of the ventricle. 

 Of this 43 mm., 28 mm. belong to the pylangium. The pylangium 

 is rather plainly divisible into three divisions, which are subequal. 

 The first division, that nearest to the ventricle, seems on a dis- 

 section to belong partly to the ventricle and partly to the truncus 

 arteriosus. Externally, however, as the drawing shows, it appears 

 to be cleai'ly a part of the truncus ; its smooth walls and sharp 

 demarcation fiom the ventricle mark it out as a portion of the 

 truncus. The synangium does not abut upon the anterior wall of 

 the pericardium as in Menohixinchus *. It divides while within the 

 pericardium into light and left halves, which separately perforate 

 the peiicai'dium. The diameter of the synangium is very much 

 greater than that of the pylangium, about twice as great, and it 

 has an almost square outline. 



The auricle is attached to the ventricle for the greater part of 

 the anterior left-hand border. 



It is naturally, on acccount of its thin walls, of somewhat 

 irregular outline. It is a little difficult to compare the sizes of 

 the auricle and the ventricle on account of their different shape ; 

 but it appeared to me that the auricle is slightly, but not very 

 distinctly, the lai-gei'. Whether the auricle does during life I do 

 not know, but it can lie entirely on the left hand of the ventricle 

 owing to the large pericardium. The sinus venosus is spacious 

 and opens into the auricle not far fi'om the opening of the latter 

 into the ventricle. It receives below and approximately in the 

 middle line the vena cava inferior. On each side opens into the 

 sinus venosus a transverse ti'unk which is, I presume, partly 

 ductus Ctivieri and partly superior caixlinal. Each transverse 

 trunk runs along the whole of the transA^erse diameter of the 

 pericardium and in contact with its posterior wall. 



The auricle is very distinctly divided into two cavities (text- 

 fig. 30). The larger, which 1 presume to be the equivalent of the 

 right auricle, lies nearest to the ventricle into which it opens. The 

 sinus venosus opens into this, and its orifice is shielded on the 

 side remote from the ventricle by a flap, which so far completely 

 partitions the auricle, since it extends from roof to floor, and has 



* Huxley, "On the Stnictuie of the Skull and of the Keavt of 3Ienohranchus 

 lateraUs," P. Z. S. 1874, p. 186. 



