MADEIRAN GROUP. 103 



ration in this species ; but in some examples there are evident 

 traces of a narrow darker interrupted (or tessellated) fascia on 

 the hinder edge of each volution, which is particularly visible 

 above the keel of the basal one, and likewise a similar one (at 

 some distance from the keel) on the underside ; and in the 

 smaller (or typical) state of the shell the peristome and the lamel- 

 liform callosity which unites its upper and lower halves preserve 

 an abruptly-defined and conspicuous reddish-yellow hue. Indeed 

 this last-mentioned peculiarity is one of the main distinctive fea- 

 tures in Pfeiffer's diagnosis ; nevertheless occasional specimens of 

 even this smaller phasis have the peristome colourless, whilst 

 the exponents of the larger race [ov fiuctuosa, Lowe) have never 

 any indication of a brilliant hue about the aperture (which is uni- 

 formly white). But, apart from its diminished size and this 

 colouring of the peristome, the typical state differs from the 

 larger one (or jluctuosa, Lowe) in having its keel less acutely 

 developed, its whorls just perceptibly more tumid, and its entire 

 surface more uneven or malleate, though rather less evidently 

 sculptured with minute oblique striae. Nevertheless, in nearly- 

 all their features, I think that the two aspects of the shell pass 

 imperceptibly into each other. Both of them also (particularly 

 however the larger one) have, as just mentioned, a slight ten- 

 dency to be freckled, or blotched, with a few opake milky 

 markings, — in all probability occupying the positions of former 

 interrupted fasciae, or patches. 



The affinities of the H. chrysoraela are manifestly with the 

 H. erubescens, Lowe ; and indeed the larger state (which I would 

 register as the ' /3. fluctuosa ') has so much in common 'prima 

 facie with the Forto-Santan phasis of the latter (or 'a. porfo- 

 sancti ') that I had at first imagined that the two might prove 

 perhaps to be but the subfossil and recent homologues of each 

 other ; nevertheless a closer inspection of them would seem to 

 imply that they pertain in reality to slightly different types, — 

 the H. chrysomela being not only more keeled and less globose 

 (which is particularly observable in the state ' ^. fluctuosa ') but 

 having likewise its columella shorter, and its lower lip straighter 

 and more horizontal, as well as much more thickened internally, 

 the iucrassated portion too extending throughout nearly its entire 

 length, instead of being gradually terminated at only a short 

 distance from the axis. 



Helix membranacea. 



Helix membranacea, Lowe, Ann, Nat. Hist. ix. (1852) 

 „ „ Pfeif., Mon. Hel. iii. 38 (1853) 



„ „ Loive, Proc. Zool. Socc LoniL 165 



(1854) 



