MADEIRAN GROUP. 233 



appreciably less developed, the third palatial plait, on the con- 

 trary, being more so, and distinctly longer. 



The latter of the two states just alluded to I would define as 

 the var. /3. pumilio ; and were it not that I appear to possess 

 examples which constitute a complete passage into the other, I 

 might have been inclined to regard it as specifically distinct 

 from (however intimately allied to) the normal P. monticola. 

 But, as it is, I think there can be no doubt that the forms in 

 question are but slightly differing races of a single species, 

 assumed respectively in the higher and the lower districts. 



The 'var. /8. pumilio' was taken in profusion by Mr. Lowe 

 and myself, on the 10th of May 1855, within crevices of the ex- 

 posed rocks, at a low elevation, on the northern coast of Porto 

 Santo, namely in the abrupt and almost inaccessible region 

 behind (and below) the Pico Branco, facing the Ilheos de Nor- 

 deste ; and several examples of it are also now before me, which 

 were obtained from Porto Santo by the Baron Paiva, but I have 

 no memorandum of the precise locality in which they were 

 found. This particular phasis of the P. monticola may be enun- 

 ciated thus : Var. /8. pumilio. Curtula, obtuse cylindrica, sub- 

 opaca, rufo-brunnea, dense costulata ; anfractibus convexis, 

 tumidulis, interdum fasciatis; apertura parvula, rotundato- 

 auriformi, distincte 6- (indistincte 7-) plicata, sc. 2 ventrali 

 (exteriore obliqua flexuosa, interiore minore immersa sed parum 

 magna), 1 columellari (superiore subobsoleta), et 3 palatalibus 

 (remotis, sed elongatis conspicuis); peristomate incompleto (sc. 

 inter plicam ventralem exteriorem et columellamlate interrupt*)), 

 labro extus subrotundato (vix sinuato), denticulo obsolete, sinu 

 parum distincto. Long. lin. 1 1J. 



Occasional large examples of this particular variety of the 

 P. monticola might at first sight be almost mistaken for abnor- 

 mally small ones of the P. corneocostata ; nevertheless the fact 

 of their peristome being completely interrupted between the 

 outer ventral plait and the columella will, apart from other mi- 

 nute characters, generally serve at once to separate them from 

 the latter. 



The P. monticola is stated by the Baron Paiva (Mon. Moll. 

 Mad. p. 134) to occur in a subfossil state at the Zimbral d'Areia ; 

 and although it is far from unlikely that this may be the case, 

 I feel that further evidence is necessary before his assertion can 

 be accepted ; for, in the first place, the Baron does not appear 

 to have even known the P. monticola properly (as is evident 

 from his doubts concerning its true distinctness from the P. 

 millegrana, a species with which it has almost nothing in com- 

 mon), whilst his confusion of the P. corneocostata with the P. 

 ferraria leads me to suspect that the former of those two spe- 



