LAURIA, CANARY ISLANDS. 117 



The lamella-like ribs, chiefly epidermal, the scarcely ex- 

 panded Lip, and the absence of any trace of a parietal lamella 

 (while the angular is strongly developed), all distinguish this 

 extremely rare shell from the other Madeiran species. 



The largest example seen is a fossil (PL 14, fig. 8). It is 

 more cylindric than any recent shell in the series of 15 ex- 

 amined. The whorls above the last are so convex as to ap- 

 pear subangular. There is no parietal lamella, and the 

 lower-palatal fold is very small. Length 2.3, diam. 1.55 mm. ; 

 5Vi> whorls. If these characters are constant in the fossil 

 form it should be separated subspecifically. 



Recent specimens are smaller and taper more. They have 

 a pale band below the periphery. The initial l 1 /^ whorls 

 are finely striate spirally, after which the riblets begin, at 

 first close, then more spaced, and generally high and thin 

 in the middle, especially in immature stages. The lip is 

 scarcely expanded, but is thickened within. The high, thin 

 angular lamella penetrates to the dorsal side. There is a 

 very low and short but quite distinct parietal lamella in one 

 of the specimens. The lower-palatal fold, though small, is 

 more developed than in the fossils. With age it diminishes. 

 The ribs become very weak or obsolete on the base. Length 

 2, diam. 1.7 mm., 5U, whorls, or slightly larger. 



In the immature stages (3 or 4 whorls) the angular and 

 columellar lamella? are well developed, and there are some- 

 times weak traces of basal barriers, tubercular or radial. 

 5 of these appear in the figure; but in some others none are 

 visible (pi. 14, figs. 10, 11). 



Species of the Canary Islands. 



These forms are related to the Azorean L. fuscidula group, 

 the L. vincta group of Madeira and to continental species. 

 There is no upper-palatal fold in any specimens I have seen, 

 and the basal fold is often lacking. The three species are 

 closely related, distinguished as follows: 



Wider; no callus between the thin angular lamella and 

 the right lip-insertion. Teneriffe. L. castanea. 



