324 



LECTLKE XXIII. 



which I have termed pericardium ; it is separated from the branchial 

 cavity by a strong membranous partition, in which the following ori- 

 fices are observable. In the middle the termination of the rectum, 

 to the right of this the orifice of the oviduct, and on each side at the 

 roots of the anterior branchiae there is a small mamillary eminence 

 with a transverse slit, which conducts from the branchial cavity to 

 one of the compartments of the pericardium containing two clusters 

 of venous glands. There are also two similar, but smaller, slits con- 

 tiguous to one another, near the root of the posterior branchia on 

 each side. These, which seem to have been overlooked in my first dis- 

 section, were detected by M. Valenciennes in the specimen of the 

 Nautilus Pompilius which he has recently described* ; and I have ob- 

 served them in that subsequently presented to the College by Capt. 

 Sir E. Belcher. They lead to the compartments which I formerly 

 described and figured f, containing the posterior clusters of the 

 venous follicles. These compartments M.Valenciennes regards as 

 shut sacs, communicating only by the above-mentioned apertures 

 with the branchial cavity. 



The venous branches, from the labial and digital tentacles, and 

 adjacent parts of the head and mouth, terminate with those from the 

 funnel in the sinus, partly excavated in the body of the cartilaginous 

 skeleton, and in part continued round the oesophagus. From this 

 sinus, the great vena cava(^^. 132. a) is continued, running in the in- 

 terspace of the shell- 

 ^•^^ F=t^3z^gj muscles on the ven- 



tral aspect of the ab- 

 dominal cavity, and 

 terminating within 

 the pericardium by a 

 slight dilatation (c), 

 which receives by 

 two veins (d) the 

 blood from the difFer- 

 ent viscera. The vena 

 cava is separated by 

 a layer of decussat- 

 ing muscular fibres 

 from the abdominal 

 cavity, which closely 

 adheres to the pa- 

 rietes of the vein. 



S'aurilus Pompilius 



♦ Archives du Museum, p. 257. 4to. 1839. 



t Memoir on the Nautilus, p. 32. 1832. Plate 5. u, u. 



