OF CONCHOLOGY. 79 



riety and cannot fail to be recognized. It is longer and nar- 

 rower than any other species and cannot be confounded with any 

 described species. All the specimens were unattached. 



The anatomy of this species will form the subject of another 

 paper. 



TRIMERELLA, Bill, and GOTLANDIA, p. 160. 



In provisionally proposing the name Crotlandia for the shell 

 figured by Dr. Lindstrom, I felt a slight doubt as to its distinct- 

 ness from Trimerella, principally because figures, and especially 

 restorations, are not infrequently insufficient representations of 

 the objects intended. Still I could hardly question the plain 

 statements in the paper alluded to. Since that time some mis- 

 apprehension as to the identity of the fossils examined by me in 

 Prof. Hall's collection having arisen, I have been indebted to the 

 kindness of Mr. Billings for an opportunity of examining various 

 specimens of Trimerella, both from Canada and from Gotland. 

 The latter were collected by Dr. Lindstrom. 



The Canadian species are all casts in a calcareous rock and 

 more or less incrusted with calc-spar. The specimens from Got- 

 land retain the shelly matter, but in a metamorphosed condition, 

 so that the shell structure cannot be determined. Besides these, 

 I have had the opportunity of examining a few specimens of 

 another species from the Niagara group, collected by the Geo- 

 logical Survey of Ohio, in charge of Dr. J. S. Newberry, and in 

 very poor condition. In these, the shell is only represented by 

 rude incrustations of calc-spar, originally made over the shell 

 which has since been entirely dissolved away. 



Although these materials are anything but complete, they still 

 afford some information. Among the Canadians specimens three 

 forms of probably specific value appear to be represented, beside 

 the species from Ohio, which appears to differ essentially from 

 the others. With regard to the Gotland shell the materials are 

 not satisfactory for a full comparison. 



One thing appears to be certain. In none of the American 

 species is there any pit, interlocking process, or hinge-teeth, such 

 as are figured by Lindstrom in his paper on the Gotland shell. 



The provisional genus Gotlandia was suggested on the sup- 

 posed differences above mentioned ; if they do not exist, it of 

 course, falls to the ground, and with it the figures and description 

 upon which the characters were based. 



On the other hand, though none of the Gotland shells have the 

 cardinal border well exposed, yet I am equally unable to discover 

 anything of the kind there ; though that it may not exist, I 

 would not be understood as asserting. Dr. Lindstrom had doubt- 



