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mentary canal, and its relations to the liver and large ovary ; and 

 describes a large viscus situated in the space between the ovary, the 

 adductor muscle, the base of the foot and the pericardium, divided 

 into a central and two lateral portions, and secreting a dark brown 

 liquid loaded with fatty matter. This body he thinks may be con- 

 nected with the secretion of the byssus, but, at the same time, 

 remarks that it may be homologous with the organ of Bojanus. 

 Lastly, the anatomy of the heart and great arteries is given, and is 

 in substance as follows. 



On cutting through the floor of the cloaca, the pericardium is laid 

 open, and in it is seen the large, rather square-shaped ventricle, with 

 a capacious but thin-walled auricle opening into it on either side, 

 through an orifice guarded by semilunar valves. From the thick- 

 walled ventricle, a short tube conducts into a conical dilatation or 

 bulbus arteriosus, with muscular walls, having its base included 

 in the pericardium, and giving rise near its narrow end to the 

 anterior and posterior pallial arteries; whilst a visceral artery 

 passes from the ventricle to the ovary and adjacent parts. As in 

 other bivalves, the intestine, before its termination, passes through 

 the heart : in coming through the pericardium, surrounded by 

 that membrane, it forms a short round pedicle which joins the fore 

 part of the ventricle ; it is then continued through the ventricle and 

 bulbus arteriosus, and finally opens into the cloaca. The blood 

 from the ventricle flows between the outer surface of the intestine 

 and the inside of the sanguiferous channel ; and " that part of 

 the intestine which traverses the bulbus arteriosus is closely sur- 

 rounded with elongated membranous valvulse, which arise from the 

 anterior part of the chamber where the gut enters, and are fixed by 

 a number of cordae tendinese to the posterior wall, where it makes its 

 exit;" a contrivance which permits the blood to pass between the 

 rectum and the little valves, but prevents its reflux. 



The description is illustrated by drawings of the exterior of the 

 animal and of the particular parts specially referred to, and also by a 

 diagram representing the general arrangement and relative position 

 of the several organs. 



