340 TEST ACE A ATLANTIC A. 



Helix retrodens, Pfeiff., Mon. Hel. vii. 347 (1870) 



Hahih'f Teneriffam ; a cl. Fritsch detecta. 



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

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

 malleatedj 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 thiekened 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) 



Pfeiff., 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, praecipue 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 //. 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- 



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