33^ jOltRNAL OF* CONCHOLOGY. 



ON THE RE-DISCOVERY OF 



PLANORBIS MULTIVALVIS. Case, and PLANORBIS 



TRUNCATUS Miles. 



By BRYANT WALKER, Detroit, U.S.A. 



In 1847 Case described the Planorbis multivalvis from specimens 

 received from ' Captain Stanard who found it in the northern 

 part of Michigan.' A single example received from Mr. Case 

 by Dr. Gould and deposited in the Smithsonian Museum was 

 apparently the only specimen preserved. And for forty years 

 no further trace of the species has been observed. During the 

 summer of 1887, however, it was the good fortune of Dr. M. L. 

 Leach of Travuse City, Michigan, while collecting at Marl Lake 

 Roscommon County, Michigan, to bring to light again the long- 

 lost species. A couple of dozen specimens were found, 

 most of which have come into my possession. Some of them 

 were submitted to the late Geo. W. Tryon, Jun., of the Phila- 

 delphia Academy of Sciences, and the identification with Case's 

 species was approved by him. Compared with P. campamdatiis 

 Say this form is broader and not so high, owing to the rounded 

 shape of the whorls. The hump directly opposite the aperture, 

 and which forms the most striking part of the original figure, 

 only occurs in a small proportion of the specimens, and 

 when present the last half whorl is irregular and distorted almost 

 as though diseased. It would seem as though the animal 

 having completed its shell was, through some unforeseen con- 

 tingency, compelled to continue it another half whorl and pro- 

 ceeded to do so in a very haphazard sort of way. It is perhaps 

 doubtful whether this species will prove to be more than a 

 strongly-marked local form of P. campamtlatus Say, but that it 

 is entitled to varietal rank at least seems unquestionable. 



Planorbis truncatus was described by Dr. Miles, State 

 Geologist, in 1861, from specimens found in Saginaw Bay in 

 the north-eastern part of the state. So far as I know none but 



J.C, v., July, 1888. 



