458 THE ANATOMY OF INVERTEBRATED ANIMALS. 



more than three-fifths of the length of the body, and is there- 

 fore much less deep than in the Dibranchiata. The anus 

 opens in the middle line on the posterior wall of the pallial 

 cavity, close to its junction with the anterior wall. The four 

 branchiae are attached, two on each side of the anus, to the 

 posterior wall of the branchial chamber, and the inner branchia 

 is shorter than the outer. The nidamental glands, composed 

 of numerous vertical lamellae, partly covered by a fold of the 

 lining membrane of the pallial cavity, are situated on the 

 posterior wall of that cavity, almost midway between its 

 union with the anterior wall and its free edge. The paired 

 renal chambers lie immediately above them also, in the pos- 

 terior wall of the pallial cavity. 



The buccal mass is very large, its length amounting to 

 one-third that of the body. The apices of the great horny 

 beaks are obtuse, and are coated with a calcareous deposit. 

 The oesophagus dilates into a wide crop and is separated by 

 a constriction from the stomach, the chitinous lining of which 

 is thick and ridged. The pyloric caecum is small and rounded, 

 and the intestine makes two bends upon itself before reaching 

 the anus. Salivary glands appear to be wanting, unless cer- 

 tain glandular bodies placed within the buccal mass should 

 be of this nature. 



The liver is a loosely racemose gland, divided into four 

 lobes, and is lodged in the anterior part of the perivisceral 

 cavity. There is no ink-bag, and there are no branchial 

 hearts. The quadrate systemic heart is situated on the left 

 side of the posterior face of the body, close to the junction 

 of the posterior with the anterior wall of the pallial cavity. 

 It receives four branchio-cardiac veins ; and, attached to it, is 

 a pyriform sac, which, according to Keferstein, opens into the 

 pallial cavity. 



The cartilaginous skeleton supports the pedal and parieto- 

 splanchnic ganglia, but does not encircle the gullet, or roof 

 over the cerebral ganglia. Two long processes of the skele- 

 ton pass into the funnel and give attachment to its muscles. 

 Two large shell-muscles are attached to it; and, passing up- 

 ward and outw r ard, are inserted into oval chitinous patches 

 visible on the outer surface of the mantle, and connected to- 

 gether by a thin ring of the same substance (the annidus) 

 which encircles the mantle. 



The oviduct does not arise directlv from the sac in which 

 the ovary is lodged, but from a distinct chamber, into which 

 the ovarian sac opens. A large albumen-gland pours its 



