CANARIAN GROUP. 401 



is satisfactory that the H. argonautula should have been met 

 with by Mr. Lowe and myself, who, by finding it (in consider- 

 able abundance) at Arguineguin in the south of Grand Canary, 

 were enabled to supply the required data concerning its precise 

 habitat. 



The H. argonautula (which measures about 4 lines across 

 its broadest part, and which is composed of about 4^ rapidly 

 increasing volutions), is a thin, sublenticular, and very acutely 

 carinated shell, the keel (which is irregularly crenulated) 

 being strongly expressed on the upper side on account of a 

 slight groove or erosion alongside it, and being usually traceable 

 up the penultimate whorl as an elevated line adjoining the 

 upper edge of the suture ; its spire is greatly depressed, though 

 with the nucleus a little prominent ; its base is suloconically 

 convex, with the umbilicus rather suddenly and deeply scooped- 

 out ; its aperture (which is obsoletely elongate-quadrangular) 

 has the upper and lower portions of the peristome acute and 

 only obscurely connected by a thin intervening lamina ; and its 

 surface is densely sculptured with coarse, irregular, undulating, 

 oblique costate lines. In colour it is of a pale corneous brown 

 (rather paler, and yellowish, beneath, particularly towards the 

 umbilicus), obscurely marbled above with cinereous lines and a 

 few fragmentary patches, and with a narrow band below (seldom 

 two) at a short distance from the keel. 



There is a certain prima facie resemblance between this 

 species and the Madeiran H. tabellata, Lowe ; nevertheless tle 

 latter is very much more flattened above, with the whorls 

 narrower and more numerous, and (although quite as acutely 

 carinated) the keel is not shaped-out (or compressed ^ by an 

 adjoining erosion on the upper side, nor is it visible on the 

 penultimate volution ; its base (although inflated) is not coni- 

 ca%-convex; its umbilicus is narrower; its aperture is less 

 angular, with the peristome less acute and slightly recurved ; 

 and its surface is less coarsely costate-striate, but studded with 

 large granules, as well as more broadly fasciated below. 



Although supposed to be exclusively Canarian, Mousson has 

 lately described (Jahrb. Malak. Ge's. i* 81 ; 1874) what he re- 

 gards as a mere phasis of this Helix from Casa Blanca in Morocco, 

 a fact of considerable importance geographically. But if the 

 Grrand-Canarian form of the species be truly the one which was 

 originally enunciated by Webb and Berthelot (which perhaps, 

 considering the unsatisfactory manner in which it was obtained 

 namely from amongst dried orchil, may be open for con- 

 sideration), it is quite clear that it must be accepted as the 

 type, and that consequently the modification from the African 

 continent (whatsoever it may be) should be treated practically 



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