SPECIAL ANATOMY. 61 



much stronger, and has its origin in common with the retractor of the 

 foot and eye-peduncles, from the columella of the shell ; at its insertion 

 it forms a semicircle around the posterior inferior part of the buccal 

 body. The pouch of the lingual lamina is always a prominent object. 

 In Zonites cellaring and Macrocyclis concava, the buccal body is propor- 

 tionately nearly twice the length of that of the other species, denoting a 

 carnivorous habit, as in Glandina. The dental plate, or jaw, varies 

 in some degree in different species : in Zonites, Macrocyclis, etc. it is 

 smooth anteriorly, and in the middle projects downwards into a large 

 conical toothlet ; in Mesodon, Triodopsis, etc. the anterior surface pre- 

 sents a number of curved ribs, each of which projects inferiorly as a 

 sort of toothlet, denticulating either margin. 



The oesophagus is generally long and narrow. In some species it is 

 xinusually long and contracted, as in M. concava, Z. cellaring, Steno- 

 trema hirsutum, Patula perspectiva, etc. ; in others it is long, and dilated 

 in the middle, as in Polyyyra auriculata ; in many it is capacious, and 

 gradually passes into the stomach, as in Mesodon exoleta, etc. It is ex- 

 ceedingly long in Polyyyra septemvolva. 



The stomach is usually cylindroid, and more or less sacculatcd. The 

 posterior cul-de-sac is always present. 



The small intestine comes off from the stomach at a very acute angle, 

 and into the latter two hepatic ducts empty. It is pretty uniformly 

 cylindrical, and forms, as in slugs, a single convolution or a sigmoid 

 curve, among the lobes of the livei", and penetrates to the pulmonary 

 cavity at its right posterior angle. The rectum, in all the testaceous 

 genera, corresponds in length to the pulmonary cavity, the right side 

 of which it occupies to the pulmonary orifice, at the outer border of 

 which it terminates by the anal aperture. It is cylindrical, usually 

 wider than the small intestine, and is frequently somewhat saccnlated. 

 Upon the outer side of the rectum, running its whole length, is a band 

 of muscular fibres, the object of which is, apparently, the retraction of 

 the collar, the shortening of the rectum, and the expulsion of its con- 

 tents. 



The salivary glands are generally elongated, oval, with lobed edges. 

 They are usually united together and situated on the oesophagus, or 

 commencement of the stomach. When the oesophagus is narrow they 

 surround it ; when dilated, they occupy one half or two thirds of its 

 surface. The salivary ducts are long and large. 



The liver is four-lobed, three of which lobes are anterior or inferior, 



