380 MOLLUSKS OF THE GALAPAGOS — STEARNS. 



The. peculiar (lovclopiiuMitol" callus, and (list<»i(c(l aperture caused 

 thereby, are jjiohably «lue to (lie deposit iou of shelly matter, limey 

 mucus or lyu4)h, at the tiuie ol" hiberuatiou, wlieu the animal has at- 

 tached itself to the twij»- or stalk of the plaut which is to be its resting 

 jdace for its season of inactivity. The stalk or twij;-, beinj;- roun<l or 

 roundish, ami (lie mouth of the shell or aperture not (ittin;;' closely to 

 the inequalities of the surface, in order to exclude the air, a deposit is 

 nnuh', and a tilliuij- in of tlie chinks <u" closing' of the j;aps ensues, and 

 jierfect adhesitui is secured as well as complete exclusion of the atmos- 

 l)here. Where, in other instances, the peculiarity referred to is less con- 

 spicuous, the adhesion duriiii;' hibernation has been to some object of a 

 ditVei'ent shape, as perhaps, (o (hesurtaceof a stalk of larger propcu't ions, 

 where the exact spot of adhesion was more nearly in plane with the 

 aperture; in such a case the gap or discrepancy between the edge of 

 till' aperture and the surface adhered to, would i'e(|uire but a slight 

 dei)Osit in order to close it or, in other words, the character of the surface 

 of the object to which the individual adheres at the time of hibernation, 

 practically molds and shapes the i)eristome or edge of the aperture, 

 the callus conforuung to the inequalities of the surface. 



B. mix, variety with crciiulatcd suture. 



Charles Island; one example (Mus. No. 122002). 



The crenulation of the suture, attributable to the batting: up of the 

 incremental lines against the base of the preceding* whorl, during the 

 juocess of growth, a not uncommon character, and an exceedingly con- 

 spicuous feature in many of (he ISouth American Bulimi of the west 



coast. 



******** 



B. mix, variety with sutural nodes. 



Chatham Island ; one example (Mus. No. 122003). 



This form properly follows the preceding; it has a slightly creuulated* 

 suture in the specimen before me; and, as well as others that I have 

 seen, is dark colored and has a sutural girdle of more or less conspic- 

 uous equidistant nodes. These sculptural characters occur doubtless 

 (|uite independent of coloration. />*. mici/onnis Petit, is referable to 

 (his variety. 



B. iiux, varieties iiileniicdiate. 



I also include in the general synonymy of iiiu; nuciila Pfr., inrdlidus 

 Keib., and vennstus Keib; the latter is apparently a. dwarfed form. 

 Tliese species of l\eibis<h's are numbered in pi. i, (igs. (> and 7. His 

 Wolji is from Indefatigable Island, upon which li. nux has not yet 



