34C TEST ACE A ATLANTIC A. 



Helix retrodens, P/eiff., Mon. Hel vii. 347 (1876) 



Habitat Teneriffam ; a cl. Fritsch detecta. 



The H. retrodens (of which I have no type for comparison) 

 is described as a rather convex, strongly striated shell, partially 

 malleated, somewhat shining, and of a pale-yellowish olive-brown 

 (still paler beneath;, and with three indistinct darker bands 

 which are more or less interrupted by whitish lines and mark- 

 ings. Its nucleus is said to be finely granulated ; and its peri- 

 stome, which is white and very broadly expanded, has its basal 

 portion thickened internally into an obtuse ridge-like plait. It 

 is stated by Mousson to be allied to the H. modesta, Fer. 

 (= Paivana, Lowe), and was taken by Fritsch in Teneriffe. I 

 possess examples of a Helix from Arona which agree to a great 

 extent with the diagnosis of the H. retrodens, though not suffi- 

 ciently so to enable me to refer them for certain to that species. 



Helix modesta. 



Helix modesta, Fer., Prodr. 71 (1821) 



55 55 Pfei/., Mon. Hel. i. 269 (1848) 



Paivana, Lowe [nee Fer., 1864], Ann. Nat. Hist. 



vii. 110(1861) 



Pfeiff., Mon. Hel. v. 307 (1868) 



modesta, Mouss., Faun. Mai. des Can. 83 (1872) 

 Pfeiff., Mon. Hel. vii. 351 (1876) 



Habitat Teneriffam ; juxta Sta. Cruz, prsecipue in Barranco 

 Santo, vulgaris. 



This is a common Helix near Sta. Cruz in Teneriffe, parti- 

 cularly in the Barranco Santo, where it was met with abun- 

 dantly by Mr. Lowe and myself, as it had been previously by 

 Fritsch ; and it was also taken by Blauner and Grasset. By 

 d'Orbigny it appears to have been mixed up, or confused, with 

 the H. Pouchet. 



The H. modesta is of a dark greenish-brown hue above, but 

 paler, yellower, and more glossy beneath, and occasionally with 

 obscure indications of a few obsolete bands. In form it is rather 

 compact and obtuse, with faint traces on its basal whorl of a 

 keel, which however completely vanishes towards the aperture ; its 

 peristome is white and broadly developed, the basal portion being 

 nearly straight but a good deal thickened ; and its surface is 

 roughened with irregular transverse costate lines, and is here and 

 there conspicuously malleated. 



As compared with the H. plicaria, the modesta is smaller, 

 more depressed, and more compact, as well as of a darker 

 greenish-brown hue ; and (although strongly costate-striate) it 

 is free from the remote and greatly elevated string-like trans- 



