CATALOGUE OF SHELLS. 215 



Planorbis bicarinatus, Say. Sault St. Marie, Black River. 



parvus, Say. Sault St. Marie. 



Valvata tricariuata, Say. Black River. 

 Amnicola grana, Say. Fort William, Cape Gourganne. 

 Paludina ponderosa, Say. Niagara. 

 Melania livescens, Menke. (niagarensis, Lea.) Niagara. 



subulata. Niagara. 

 Cyclas similis, Say. Sault St. Marie. 



" partumeia (young) ? Say. Fort William. 

 5 Pisidium dubium, Say. Fort William, Michipicotin. 

 Unio radiatus, Gmel. Northern shore. 

 Anodonta Pepiniaua, Lea. Northern shore, Cape Gourganne. 



The number of bivalve shells seems to diminish very abruptly at the chain of 

 the great lakes; so that of the great number of species, so profuse also in the 

 number of individuals, in the States bordering on the south, scarcely ten spe- 

 cies, and those not abundant, are found to the north ; and all these are meagre 

 in development, and of the simplest form and color. 



obliquis, ultimo f testae eequante ; apertura angusta, dimidiam longitudinis fere ade- 

 quante, postice acuta, plica columellari conspicua, acuta, vix spiral! ; labro fascia cas- 

 tanea submarginali picto. Long, f , lat. ^, poll. Proceed. Bost. Soc. Nat. History, 

 III. 64. Oct. 1848. (See pi. 7, figs. 8 and 9.) 



A medium sized species, with an elongated, delicate, minutely reticulated shell, com- 

 posed of about six very oblique flatfish whorls, the last of which constitutes three fourths 

 of the whole shell. The aperture is narrow, having a sharp, slightly winding fold on 

 the pillar, and a submarginal brown stripe just within the lip. 



Next to L. gracilis, this is the most delicate species we have. It may be compared 

 with L. attenuata and L. reflexa, from both of which it differs in the flatness of its 

 whorls, in its narrow, elongated aperture, and in being only half their size. It is much 

 like Physa hypnorum reversed. 



5 PISIDIUM DUBIUM. The separation from Cyclas of some species under the name of 

 Pisidium being regarded as legitimate, I place this shell under that genus. The shells 

 brought from Lake Superior seem, however, to differ somewhat from specimens from 

 the Atlantic region. They are smaller, more elevated, less sulcated, and the hinge is 

 less robust. I had designed to apply to them the specific name P. tenellwn, but un- 

 fortunately the specimens were mislaid before I had examined them with sufficient 

 care to give the characters with the requisite precision. 



