INCISURA (sCISSURELLA) LYTTELTONENSIS. 21 



groove of the Trocliid^e, and it has the same relation to the 

 liver-ducts. It should be noted in this place that Incisura, in 

 the possession of numerous biliary apertures, resembles 

 Fissurella and differs from Trochus, which has two, and 

 Pleurotomaria, which has only one bile-duct. The intestine 

 leaves the stomach on the ventral side of the anterior third of 

 the stomach in Incisura. Beyond it the stomach narrows 

 rather abruptly, and is continued forward as a small caecal 

 diverticulum, the front end of which is inserted in the loop 

 formed by the left-hand bend of the rectum. The walls of 

 the blind end of this diverticulum are covered internally by a 

 thick chitinoid layer, and thrown into complicated folds and 

 ridges, but the cEecum is not spirally coiled, and situated as it 

 is at the end of the stomach furthest from the bile-ducts, it 

 cannot be homologised Avith the spiral caecum of Pleuroto- 

 maiua, Haliotis, or Trochus. It must, however, be the cgecum 

 referred to by Pelseneer (12). The walls of the intestinal end 

 of the stomach of Incisura have the columnar cells with 

 striated borders and thick cuticle so fully described by 

 Randies for Trochus. 



The intestine is provided tln'oughout its length with a 

 single longitudinal ridge or typhlosole. On leaving the 

 stomach it makes a sharp bend fi'om left to right, passes 

 vertically upwards to above the level of the stomach, thence 

 turns sharply to the right, describes a wide loop on the right 

 hand, as shown in fig. 3, and bending sharply again to the 

 left, passes nearly straight across the body till it reaches the 

 left-hand corner of the pericardium, when it turns upward 

 and to the right in the mantle roof, and becoming rectum, 

 traverses the pericardium in its diagonal passage across the 

 roof of the mantle-cavity to end in the anus opposite the 

 mantle-slit. 



The liver cseca, as may be seen in figs. 3 and 11, are few 

 in number, of relatively large size, with lai'ge lumiua bordered 

 by large secretory cells. As far as I could determine they 

 do not branch, but have somewhat convoluted courses, and 

 open independently into the oesophageal end of the stomach. 



