No. 109.] 181 



Oi\ THE GENUS TELLLXOMYA, AND ALLIED GENERA; 



WITH ILLUSTRATIONS : 



BY PROFESSOR JAMFS HALL. 



[ From Ihe Canadian .Naturalist and Geologis^t : Conducted hy E. Killings. ] 



In the investigations of palaeozoic fossils, it often happens that 

 the most important parts for the determination of the generic 

 characters are obscured or entirely hidden by the adhering stony 

 matter : this is particularly true of the Gasteropoda and Lamelli- 

 branchiata, and the generic characters are often necessarily de- 

 rived from the external features of the shell. It is not always 

 possible to make these determinations with such accuracy that 

 further discoveries will not show the necessity of some modifica- 

 tion. Were the descriptions of the genera and species of the 

 lamellibranchiate shells of the palaeozoic rocks left until the 

 hinge and teeth, the pallial and muscular impressions, could be 

 determined, comparatively few would be described. 



In the first volume of the Palseontology of New-York, several 

 new genera were proposed, and among them the Genus Tellino- 

 MYA, which is the subject of the present notice. This genus was 

 constituted to include several species, supposed to be related to 

 each other from external characters : these characters were sug- 

 gestive of Tellina and of Mya, and the name adopted accordingly. 



In the specimens known to me at that time there were no 

 visible teeth or crenulations in the hinge-line, and this fact was 

 stated in the description. Subsequently I obtained some specimens 

 which suggested other relations than those indicated by the 

 generic name. No opportunity has occurred of correcting the 

 original description ; w^hile in the mean time the species have 

 been referred by palaeontologists to other genera, and in some 

 instances to those of very different character*. 



* M. d'Orbiony refers the species of Tellinomya, described in the first volume of 

 the Paleontology of Xew-York, to the Genus Lyonsia of Turton, a modern shell 

 belonging to a very different family ; and to add still more to the confusion, the 

 same author has placed the species Modiolopsis also under the Genus Lyonsia. In 

 this reference he has been followed by one American author, who. " for a corrected 



