772 PROP. G. C. BOURNE OX THE 



oesophagus, and then turning upwards and forwards describes one 

 or more convolutions before it passes into the large intestine. 

 The small intestine can always be distinguished by its white 

 colour and narrow diameter ; it A^aries considerably in length in 

 dijSerent species, being \ongest in Alcadia palliaia a.\K\ Orobophcaia 

 ponsonhyi, shortest in Euto'ochatella pulchella. Internally it is 

 lined by a columnar ciliated epithelium containing a few gland- 

 cells, and its internal surface is increased by a well-marked 

 internal ridge or typhlosole formed by long ciliated cells. The 

 small intestine passes abruptly into the large intestine, the latter 

 being of much lai'ger diameter and having pigmented walls. In 

 all species of Alcadia and Helicina examined, the large intestine 

 runs forward and to the left below the oesophagus, then bends 

 abruptly back, forms a wide cix'cular loop w^hich passes above the 

 oesophagus, in front of the anterior end of the stomach and along 

 the inner wall of the anterior end of the pei'icardial cavity: it then 

 turns downwards and to the right, passes right round the lower side 

 of the stomach, and mounting upwards again behind it runs in the 

 right side of the roof of the mantle-cavity to open by the anus, 

 opposite the right tentacle. In the first part of its course, i. e. in 

 the short length between the small intestine and the recurrent 

 circular loop, the large intestine is lined by very evenly disposed 

 columnar ciliated cells, among which I could not detect any 

 gland-cells, and this part of the intestine is not, as a rule, full 

 of faecal matter. This section of the intestine may be described 

 as the large intestine propei', to distinguish it from the rectum, 

 into which, however, it passes without any obvious line of 

 demarcation. The i-ectum is always full of fsecal debris, and its 

 epithelium consists of (1) columnar ciliated cells ; (2) goblet- 

 shaped gland-cells filled with coarse granules which stain deeply 

 in hgematoxylin and are therefore probably mucinogenous ; 

 (3) smaller gland-cells containing small yellow gi-anules. There 

 is no typhlosole either in the large intestine or the rectum. 



Noticing that the coils of the gut differed in the different 

 species, I have been at some pains to work out this character in 

 detail, and figs. 10 to 15 (PI. XXXII.) show the coils charac- 

 teristic of six different species. An examination of the figui'es 

 will give a better idea of the differences than any description. 

 It will be noticed that there are three main types. In Alcadia 

 palliata, A. hoUandi, OrobopJiana ponsonhyi, and Palceohelicina 

 the intestinal coils, though differing in detail, are alike in this 

 respect, that the small intestine runs back more or less parallel 

 to the oesophagus over the dorsal surface of the stomach, and 

 the large intestine makes abend to the right below the oesophagus 

 and then, turning back on itself, makes a second bend to the 

 right above the oesophagus. The second type of arrangement 

 is shown in Lucidella aureola (fig. 14). In this species the 

 oesophagus is not pressed against the dorsal surface of the 

 stomach, but runs obliquely down to it ; the small intestine 

 passes forward from the pyloric end of the stomach, crosses over 



