THE CYCLOPHORID LAJSTD MOLLUSKS OF AMERICA 107 



KEY TO THE SPECIES OF SUBGENUS POTERIA 



Upper surface of last whorl corrugated. 

 Shell helicoid. 



Penultimate whorl with wrinkles. 



Wrinkles and pits coarse burringtoni 



Wrinkles and pits not coarse imitator 



Penultimate whorl with axial riblets only lineata 



Shell depressed-helicoid. 



Umbilical keel strong corrugatissima 



Umbilical keel obsolete pallescens 



Upper surface of last whorl not corrugated. 



Axial riblets almost lamellar jamaicensis 



Axial riblets not almost lamellar. 



Whorls flattened near summit plana 



Whorls not flattened near summit crassa 



This key does not include Chitty's Gyclotus nodosus^ notafus, and 

 inutilU^ specimens of which I have not seen. I have copied Chitty's 

 descriptions and offer suggestions as to their relationship under 

 each of these species. 



POTERIA (POTERIA) BURRINGTONI, new species 

 Plate 16, Figxjbes 31-33 



Shell rather large, helicoid, covered with a chestnut-brown perios- 

 tracum. The nucleus consists of 1.5 inflated, well-rounded, smooth 

 turns. The postnuclear whorls are inflated and strongly rounded; 

 the first is marked by rather strong axial riblets, which are not quite 

 so wide as the spaces that separate them. On the succeeding turns 

 these axial riblets become somewhat weakened, irregular in strength 

 and disposition. In comparison they are here narrower and more 

 elevated. Beginning with the third whorl, strong axial wrinkles 

 make their appearance. They are at first rather irregular, but on 

 the first half of the last whorl they assume a decidedly obliquely 

 slanting retractive form. These wrinkles render the upper surface 

 decidedly rough. Suture well impressed, except that of the last turn, 

 where the summit of the whorls is appressed to the preceding turn. 

 Periphery well rounded and marked by the continuation of the 

 oblique wrinkles described for the spire. These wrinkles also extend 

 over the low rounded base to the umbilical keel. They become weak- 

 ened toward the aperture. Base openly umbilicated, with a rounded 

 keel marking the outer limit of the umbilicus. The umbilical wall 

 bears rather strong axial ribs, which are crossed by incremental lines. 

 These ribs look as if they might be the continuation of the oblique 

 wrinkles. Aperture subcircular, oblique, decidedly protracted into 

 an angle at the posterior angle ; peristome somewhat sinuous ; that of 

 the outer lip thin, while that of the inner lip is somewhat thickened. 

 Operculum typically poterid. 



