MODIOLA. 



external termination^ and applied by the foot of tlie 

 animal. 



The recent species of Modiola are not very numerous ; 

 wehave, however^ several species on the coasts of Britain, 

 of which the most remarkable are the M. discrepans and 

 discors,* these two, together with some others that re- 

 semble them in form, differ much from the common 

 Modiolae, and might perhaps with propriety be considered 

 as a distinct Genus. Of fossil species there are not 

 many, such as we know seem to belong principally to 

 some beds of the Oolite series, there are others in the 

 principal formations, both above and below the chalk. 



Fig. 1. Modiola Tulipa. 



2. semifusca. 



3. - plicatula. 



♦ Tliese we believe are on our coasts always found imbedded in the common 

 Ascidia, and appear to be destitute of a byssus, while the much larger specimens 

 that are brought from the West Indies are found completely enveloped in a fine 

 silky byssus closely matted together and forming large bundles. Some cognate 

 species, however, that have been 1)rought from the Northern ocean appear to 

 have been affixed by a few filaments only. 



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