88 II 'STACK A ATLANTIC A. 



The P. placida is, <>n the average, a trifle larger than the 

 pusilla, and it is also less depressed, or more turbinate, — the 

 spire being comparatively elevated. It is usually too of a pale 

 olivaceous brown, there being nearly always either a green or a 

 yellowish tinge; and its surface, which has a somewhat sericeous 

 appearance, is very densely and regularly crowded with minute 

 hair-like lines, — unmingled with any coarser ones, such as are 

 more or less conspicuous in the P. pusilla, and which are at 

 times even sublamelliform. 



The P. placida is a little smaller than the common European 

 P. pygmcea, and with at least one volution less, its umbilicus 

 is relatively not so large, and its colour is altogether different, — 

 the pygmcea being usually of a dark coffee-brown. The stria? 

 also of the pygmcea, at any rate those on the underside, are 

 more oblique. 



(§ Acanthinula, Beck.) 



Patula pusilla. 



Helix pusilla, Loice, Cambr. Phil. 8. Trans, iv. 46. t. 5. 

 f. 17 (1831) 

 „ „ Pfeiff., Mon. Hel. i. 101 (1848) 

 „ servilis, Shuttl, Bern. Mitth. 140 (1852) 

 „ „ Pfeiff., Mon. Hel. iii. 101 (1853) 

 „ pusilla, a. annulata, Lowe, Proc. Zool. Soc. Load. 176 



(1854) 

 „ „ Alb., Mai. Mad, 18. t. 2. f. 7-10 (1854) 

 „ servilis, Morel., Hist. Nat. desAcor. 173. t. 3. f. 6 (1860) 

 „ „ Paiva, Mon. Moll. Mad. 79 (1867) 

 „ hypocrita, Dohrn., Mai, Bldtt. 1 (1869) 

 Patula servilis, Mou88., Faun, Mai, des Can. 25. pi. 2. 



f. 13-16 (1872) 



Habitat Maderam, et Desertam Grrandem ; sub lapidibus, 

 necnon in fissuris scoriae, prsecipue in aridis inferioribus, latens. 



As already mentioned, this extremely minute Patula is the 

 type of Mr. Lowe's Helix pvsiUa, — the rather larger, less de- 

 pressed, and olivaceous P. placida, which was mixed up with it 

 by him, having been separated in only his later catalogue (under 

 the name ' var. ft. sericina') as at any rate a distinct form. 

 Mr. Lowe's original diagnosis (in 1831) seems to have been 

 drawn out from the typical (or smaller) shell; whilst his 

 ' Habitat in Maderse sylvis ' manifestly applies to the larger 

 one, — afterwards treated by him as the ' var. ft. sericina,'' but 

 previously published by Shuttleworth (in his Canarian diagno- 

 ses) under the name of H. placida. The pusilla proper, which 

 is smaller, browner, and more depressed than the placida (or 



