268 BULLETIN 181, UNITED STlATES NATIONAL MUSEUM 



and in other allied species. I have at present only seen a single speci- 

 men." 



Sowerby's figure shows very strong axial ribs on the last whorl, 

 which crenulate the angulated periphery. 



Sowerby's figure has 5 whorls and measures : Height, 20 mm. ; greater 

 diameter, 36 mm.; lesser diameter, 26.8 mm. Height of aperture, 

 15.4 mm.; diameter, 15 mm. 



Subgenus CYCLomDALGOA Bartsch (antea, p. 136) 



Aperostomas of helicoid shape with closely crowded axial riblets. 



Type: Aperostoma {Gyclohiddlgoa) translucidum (Sowerby). 



Distribution : Colombia, Venezuela, British Guiana, Trinidad, and 

 Margarita Island. 



The radula oi A. (C.) translucidum trinifense, according to Guppy, 

 has the formula 3:3:3:3. The verge of A. (C.) translucidum he- 

 jumense (H. B. Baker) is on the back of the neck behind the tentacles, 

 and bears a seminal groove and a short terminal appendage. 



APEROSTOMA (CYCLOHIDALGOA) BELLI (Beddome) 



This species is differentiated from all the other Cyclohidalgoas by 

 its gigantic size. It embraces the two subspecies that follow : 



KEY TO THE SUBSPECIES OF APEROSTOMA (CYCLOHIDALGOA) BELLI 



Greater diameter more than 50 mm belli 



Greater diameter less than 44 mm haughti 



APEROSTOMA (CYCLOHIDALGOA) BELLI BELLI (Beddome) 



Pi^\TE 30, Figure 23 



1908. Neocyclotus helli Beddome, Proc. Malac. Soc. London, vol. 8, pp. 20-21 

 (fig). 



We have not seen this subspecies and quote Beddome's description 

 and copy his figure. 



"Shell openly but rather narrowly umbilicate, turbinately de- 

 pressed with conical spire, solid, of a rich chestnut-brown, somewhat 

 paler underneath and at the sutures; whorls five, convex, the first 

 four gradually increasing, the last veiy large, the two apical ones 

 smooth and shining, the others with prominent close oblique trans- 

 verse striation; aperture obliquely subcircular; peristome simple, 

 thick, sinuate at the suture ; operculum shelly, nearly flat, six-whorled. 

 Diameter 51, height 32 mm. ; aperture 25 mm. 



'"'"Hah. — Colombia, in dense forests near Zaragoza, at 800 feet 

 elevation. Lately discovered by Mr. Ernest Bell." 



It is apparently closely related to A. (C.) h. haughti, but the 

 measurements cited by Beddome are much larger than haughti. 



