THIC AXATOMY OK MK(i ALATFiACTUfS — KKSTKVEV. 439 



There is no snout, and the tentuclo lobe is far forwardi so 

 that the orifice of the pi'oI)oscis-sIieatli is close down to the front 

 niari:;in of the propodiiuii. 



The fi'itfdc/i's are short and are suddtjnly reduced in diameter 

 above the position of the eyes. 



The colaitidlar muscle is fairly long, though not very thick ; it 

 extentls up the visceral coil as far as the posterior end of the 

 pericardium. 



The mantle is thick and tough anteriorl}^ and along the sides, 

 but over the body rather thin. 



The si phonal /old is long, thick and tough; it may evidently 

 be protruded for some little distance. 



2. Pallial complex. 



The pallial cavity as usual is co-extensive with the dorsal 

 surface of the body, and is bounded at the posterior end by the 

 nephridium. 



The osphradiuin is large, situated well forward on the left-hand 

 side of the cavity, .of oval shape, and dtxrk green colour. 



The ctenidium is also large, and a prominent organ on the left 

 side of the cavit}'' ; it is of a flesh-pink colour, and extends fi'om, 

 on a level with the anterior end of the osphradium, almost to the 

 posterior boundary of the cavity. 



The hypobranchial mucous gland is well developed, and may 

 have a much folded surface. 



The rectum and uterus, or vas-deferens, lie parallel with one 

 another on the right side. 



The cavity may or may not contain a ureter at the posterior 

 end. 



5. Digestive system. 



The proboscideal complex consists of three well differentiated 

 parts. 



A proboscis-sheath, neither invaginable nor evaginable, but 

 firmly attached throughout its length, to the dorsal body wall. 



A jjroboscis-sac, probably slightly evaginable, and containing 

 the:— 



Proboscis, which is protrusible and retractile, but not invagin- 

 able. 



The mouth, situated at the end of the proboscis, opens into the 

 small buccal cavity. 



The radula is of the Fusacea* type. The pi"esence of only one 

 cusp on the laterals of J/, aruanus is of very secondary importance. 



The cesophagus, owing to the great length of the proboscis, is 

 very long ; it consists of anterior and posterior sections. The 



* Troschel— Das Gebiss der Schnecken, ii., 1S6S, pp. 69-86. 



