32 TIIK NAUTILUi^. 



2, 1887), wliicli also includes ('. rata Q. ct G. Witli the identification- 

 of the true shell of Corolla, this name becomes unnecessary, and 

 Corolla resumes the generic rank I assigned to it, with the addition 

 of a second species, Corolla calceola Verrill (sp.) from the eastern 

 coast of United States ; Cymbuliopsis becoming in its turn a synonym. 

 The details of structure I hope to publish later with illustrations ; 

 the object of this note is merely the rectification of the synonymy. 

 In a general way I should be indisposed to claim priority for a name 

 which was imperfectly characterized in publication, but Dr. Pelseneer 

 has set the example by adopting Gleba, which stands in exactly the 

 same predicament and as it is really the best plan (except in ver}'" 

 glaring cases) to take the first identifiable name, I follow his exam- 

 ple. 



THE SHELL-BEARING MOLLTJSCA OF RHODE ISLAND. 



BY HORACE F. CARPENTER. 



173. — Sphceriiun sulcatum Lam., 1818. 



This, the largest species of the genus in America, is widely dis- 

 tributed throughout Xew England, and the Middle and Western 

 States and Canada, and inhabits rivers and large ponds. It presents 

 much variation in size and color. It has been known best in this 

 country by the name of Cyclas similis Say, but Lamarck's name 

 has priority. The animal is white with liglit orange siphons. The 

 shell is transversely oval, nearly equilateral, very light for its size ; 

 valves convex, broad across the beaks, which are but slightly 

 elevated above the general curve of the shell ; interior bluish ; ex- 

 terior dark chestnut ; surftxce concentrically wrinkled with strongly- 

 raised lines, with a broader band corresponding to each year's 

 growth. Length, iV, heighth, A, breadth, i, inch. The young shells 

 do not resemble the adults, and might well be mistaken for another 

 species; they are thin and compressed, with both ends truncated and 

 resemble rhomboideum ; in ftict most of the specimens in cabinets 

 labeled rhomboideum are simply the young shells of sulcatum.. 

 The color of the young shells is lemon-yellow, but as they grow 

 older a dark shade appears at the beaks and gradually spreads 

 downwards until it covers the entire surface. In intermediate stages- 

 there is a vellow zone on the lower marofin. Thev are found in R. 



