THE NAUTILUS. 77 



originating above the shoulder angle ; body regularly sculptured with 

 spiral strife and rows of nodules ; spire elegant, high, without varices; 

 suture suddenly, vertically ascending at aperture ; eolumellar callus 

 thinning rapidly, or with an impressed area, posteriorly; no conspic- 

 uous periostracum. 



S. auris-diance, melanostomus, aratrnm, australis. 



Distribution : Mauritius to Japan and Polynesia. 



The American forms and tricornis, included by Tryon, differ con- 

 siderably (note the italicized passages above) from this very natural 

 little Lido-Pacific group, and are grouped elsewhere. 



GROUP B (nov.). 



Canal bent back, the columellar callus terminating below in a prom- 

 inent knob, giving a bilobed appearance ; lip with the antesinual lobe 

 directed forward, the outer margin inrolled and thickened, descending 

 from the suture and lobed in the posterior sinus ; body with spiral 

 rows of squarish nodules; spire moderate. 



S. papilio, lentiginosus. 



Distr. : Zanzibar to Polynesia. 



The wide difference between these two species and the smooth ones 

 allied to laciniatus is readily seen from the above definition, while 

 many points of resemblance with Group A will be detected, suggest- 

 ing community of origin. 



Sub-group B 2. 



Callus prominent below, hardly knobbed ; lip edge sharp, "hooded" 

 posteriorly, but not lobed; spire high, nodular. 



S. grnnnlatiis. 



Panama and Galapagos. 



This species, which differs utterly from all other American forms, 

 agrees too closely in many respects with the lentiainostis group, and 

 seems to form a geographically isolated section. 



GROUP C (Strombus). 



Sh^ll large and strong; canal not much lengthened, somewhat 

 curved or sin/ions; lip widely expanded, especially above, where it is 

 sometimes lobed ; suture ascending at aperture ; body spirally corded ; 

 periostracum thick and coarse, spirally wave-striolate. 



S. galhis, gigas, goliath, costatus, integer, bituberculatus, bubonius, 

 galeatus, peruvianus . 



Distr.; American, South Carolina to Brazil, Mazatlan to Peru; 

 West African. 



