140 Ainencan Seashells 



3. Umbilicus closed by the callus, which passes smoothly into the base. . 



(subgenus Idioraphe) 



A. Periphery strongly carinate; 2 mm.; Destin, Florida. 20 fms. 



gonio gyrus Pils. and McG. 



AA. Periphery rounded or indistinctly rounded. 



B. Surface spirally striate: 



C. Umbilical callus extremely convex and thick; 2 mm. Palm 

 Beach to Cape Florida pilsbryi McGinty 



CC. Umbilical callus strong, slightly convex: 



D. Strongly spirally striate throughout; 2.3 mm.; Key 



Largo clavium Pils. and McG. 



DD. Weakly striate above only; 1.5 mm.; southeast Florida 



nesaemn Pils. and McG. 



BB. No Spiral striations. 



C. Diameter 1.8 to 2.2 mm.: 



D. Rather globose, h/d ratio 75; shore to 50 fms.; south- 

 east Florida parvicallum Pils. and McG. 

 DD. Depressed, h/d ratio about 50: 



E. Callus large. Lake Worth 



obtectum Pils. and McG. 



EE. Callus small. Biscayne Bay, shore 



biscaynejise Pils. and McG. 



CC. Diameter 0.7 to i.o mm.; callus thick; Lower Keys, shore 

 lereiJiujn Pils. and McG. 



Superfa??iily CERITHIACEA 



Family TURRITELLIDAE 



Genus Tachyrhynchiis Morch 1868 



Tachyrbynchiis erosinn Couthouy Eroded Turret-shell 



Plate 21I 



Nova Scotia to Cape Cod, Massachusetts. Alaska to British Columbia. 



% to I inch in length, elongate, M as wide; 8 to 10 rounded whorls. No 

 umbilicus. Aperture round; columella smooth, slightly arched. Whorls with 

 5 to 6 smooth, flat-topped, spiral cords between sutures. Color cream to 

 chalky-white, with a thin, polished, gray-brown periostracum. Operculum 

 round, multispiral, chitinous, dark-brown. Common from 10 to 75 fathoms. 



T. reticulatum Mighels (Arctic Ocean to Maine; and Alaska) is similar. 



