OP CONCnOLOGY. 133 



Three species inhabit Louisiaua, and are the only Strepo- 

 matidse reported from that State. Neither of them occur east 

 of the Mississippi. 



G. semicarinata, one of the species of this division, extends 

 from Tennessee and Kentucky, throughout all the Western 

 States and the Lakes, and rejoices in twelve synonyms ! 



There are eight striate species, of which one, O. Vtrginica, 

 Say, is the only Goniohasis inhabiting the rivers of New 

 York, Pennsylvania and Maryland. Through the Erie canal 

 it is extending to the Western Lakes.* 



Very close relatives to this shell are latitans, Anth., and 

 sulcosa, Lea, the former from Green Eiver, Ky., and the latter 

 from Tennessee. 



There are over sixty species in the group which I have 

 designated as " compact, ponderous," for want of a better 

 name. They are essentially a distinct group from the other 

 Goniohases, and all the species, except three, are peculiar to the 

 branches of the Alabama River. 



ANCULOSA. 



Thirteen species inhabit the Coosa River, three of which 

 are common to the Tennessee, and one of them, A. j^rserosa, 

 extends northward to the Ohio. Two others are peculiar to 

 the Tennessee. Three species are found in the Dan, Roanoke 

 and Tar Rivers. 



A peculiar group of shells, possessing an inflated form and 

 much lighter texture, are found in the Potomac and Susque- 

 hannah Rivers, the Kanawha and the upper Ohio. They are — 

 A. dissimilis, dilatata, costata and trilineata. 



Concluding Observations. 



In studying the species of Strepomatidse^ especial care must 

 be taken not to consider young shells to be adult species. All 

 of our conchologists who have described species of this 

 family have fallen into this error. The aspects assumed by 

 young or half-grown shells, are frequently so very different 

 from their appearance when mature, as to be liable to mislead 

 experienced naturalists. 



All quite young shells are characterized by a thin texture, 

 very light color, and very sharp, acuminated spire, and in most 

 cases by the base of the aperture being acuminate also. 



Neirly every species, even when smooth, in its adult state, 

 presents the first few spires either sharply oarinate, or plicate, 

 or striate. Occasionally they are either one or the other in 

 the sime species. Hence, in describing shells as carinate, or 



* Vide Dr. James LeAvis, Proc. Acad. Nat. Sci. 



