32 THE NAUTILUS. 
2, 1887), which also includes C. vata Q.& G. With 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 asynonym. 
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 very 
glaring cases) to take the first identifiable name, I follow his exam- 
ple. 
THE SHELL-BEARING MOLLUSCA OF RHODE ISLAND. 
BY HORACE F. CARPENTER. 
173.—Spherium suleatum Lam., 1818. 
, 
This, the largest species of the genus in America, is widely dis- 
tributed throughout New 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 light 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 ; surface concentrically wrinkled with strongly- 
raised lines, with a broader band corresponding to each year’s. 
growth. Length, 74, heighth, 3, breadth, 4, 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 fact 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 yellow zone on the lower margin. They are found in R. 
