1898.] STSTEiL OF THE CHIEOPTEBA. 67 



is seen to be sculptured in low relief over the greater part of its 

 extent with a series of muscular bands running parallel to each 

 other at a little distance apart, joined with cross bands and termi- 

 nating on a Avell-marked crista terminalis. These musculi pectinati 

 are stouter and better marked in the appendix than elsewhere. 

 There was no representative of the " tubercle of Lower." 



Three main venous trunks open into the atrium. The aperture 

 of the right precaval vein is the most anterior ; at some little dis- 

 tance behind is the opening of the postcaval, guarded by the 

 Eustachian ^alve. here a thin fenestrated membrane, continued on 

 to the isthmus Yieussenii as in mau. (Fig. 6, p. 68.) Just above 

 the auriculo-ventricular opening is the entrance of the left precaval 

 vein, separated from the postcaval by a well-marked muscular 

 shelf, the valve of Thebesius being entirely absent, as £dse ^ also 

 found. Two or three ventral cardiac veins run forward over the 

 right ventricle to open directly into the auricle, and two or three 

 dorsal veins, one larger than the rest, open into the transverse 

 part of the left precaval. 



The Right Ventricle is folded around the left ventricle, and the 

 interventricular septum encroaches on its cavity, so that the 

 outline in transverse section is crescentic. 



The conns arteriosus is markedly prolonged, formi?ig a very 

 cbai'acteristic feature in the Chiropteran heart, and even more con- 

 spicuous in Pteropus edulis (fig. 3, p. 65) than in this species. 



The inner surface of the ventricular vrall is quite smooth and 

 uniform except where it meets the septum, where a few very small 

 irregularities remain. No musculi papillares arise from the ven- 

 tricular wall ; a very slender moderator band alone takes origin here 

 and passes to the septum. 



The aiu"iculo-ventricular valve has developed on a somewhat 

 different plan from most other Mammalia, resembling the condition 

 figured by Eay Lankester ^ in the Eabbit. It is composed of two 

 separate segments, the outermost and ventral of these being con- 

 siderably the larger, representing the infundibular and marginal 

 parts of the usual tricuspid valve. Arising from the interven- 

 tricular septum to supply this segment are four musculi papillares, 

 each sending 3-4 chordae tendiueae to be inserted into the free edge 

 of the valve, the adjacent chordae being continued upward on the 

 outer surface to form an arch ^, as shown in fig. 5, p. 68. 



The innermost segment is closely applied to the septum. Many 



^ EosE, C, loc. cit. 



^ P. Z. S. 1882, pp. 535-544, pi. xxxviii. figs. 3 and 4. He considers the 

 auriculo-ventricular valve in this animal to he a further development from the 

 original condition preserved in man and most mammals. If this view be 

 adopted, the valve in Fteropus might be considered to occupy an intermediate 

 condition. On the origin of the musculi papillares from the septum, see 

 Rose {loc. cit. pp. 84-85), who remarks that it is a point of no morphological 

 importance. 



' KiJESCHNER (Wagner's Handworterbuch, p. 47) describes a similar arrange- 

 ment of chordae tendineee in the human heart as an uncommon abnormality. 

 Class 1 of his division is unrepresented in the heart of Pieropjis. 



5* 



