HELIX-ISOMERIA. 143 



coluruellar margin much dilated, appressed, covering the umbilicus. 

 (Hidalgo.) 



Alt. 34, diam. maj. 71, min. 56 mill. 



Ecuador. 



H. aequatoriana HIDALGO, Journ. de Conchyl. 1867, p. 307, t. 8, 

 f. 2. PFR. Monographia v, p. 500. 



This species is allied to H. calomorpha Jonas and faunus Phil, in 

 the ensemble of its characters, but is abundantly distinct specifically. 

 The tooth of the aperture is small and acute. It approaches H. 

 atrata Pfr., but is distinguished by the larger size ; the color brown, 

 not blackish-green, and finally the aperture is quadrangular, not 

 subtrlgonal-lunar. Furthermore, the peristome is a fleshy-brown, 

 not white. This last character is rather unimportant, however. 

 (Hidalgo.) 



H. SCALENA von Martens. PL 61, figs. 1-3. 



Depressed, obtusely angular, pretty thick, the lines of growth 

 making oblique striae and where well-preserved granulate, with 

 yellowish-brown periostracum, beneath which it is chestnut-brown ; 

 whorls 5, forming a low conical blunt spire ; the three uppermost 

 plane and apparently acutely keeled, the keel filling the suture 

 which is therefore plane ; the penultimate and last whorls more con- 

 vex, the suture deeper, bluntly keeled at the periphery, more con- 

 vex beneath than above ; below the keel there is a zone of more or 

 less numerous malleations or indentions. The last whorl widens 

 very decidedly and regularly for its first half; then it becomes nar- 

 row, the peripheral angle disappears, and the base more convex, so 

 that what space is lost in the width is made good in the depth of the 

 whorl. Immediately behind the peristome the whorl is narrowed 

 vertically, making a constriction ; and this together with the lateral 

 narrowing of the whorl makes the aperture small in proportion to 

 the size of the shell. The aperture has a peculiarly displaced aspect, 

 as if it were compressed in the direction of the smaller diameter ; it 

 is very oblique ; peristome thickened, narrowly reflexed, reddish- 

 yellow ; terminations remote, connected by a distinct parietal callous ; 

 upper and outer margins short and arcuate, lower margin long and 

 straight, separated from the outer lip by an angle, widening toward 

 the umbilicus ; umbilicus pretty wide, but completely covered by a 



