Anculosae of the Alabama River Drainage 



51 



Measurements of shells: 

 Altitude Diameter 



9^4 mm- Cahaba River, Aldrich collection 



Calkins collection 



Henry Ellen, Jefferson County- 

 Lily Shoals, Bibb 



Ancnlosa melanoides (Conrad) 



Fig. 28 



Anculotus melanoides Conrad, New Fresh Water Shells of U. S., p. 64, 1834. , 

 Anculosa iurgida Hald., Supplement to No. i, Monog. Limniades, Oct. 1840. 



Conrad's description of melanoides, like most of the other early descrip- 

 tions of the Pleuroceridae, is indefinite and incomplete. The diagnosis 

 might fit many other species of the family. The locality given, "inhabits 

 rivers in North Alabama," also lacks definiteness. The foregoing comments 

 apply as well to Haldeman's tnrgida. In the absence of type specimens and 

 a clear description, reliance is placed upon Tryon's identifications and his 

 illustration in recognizing the smaller of the two Black Warrior Ancul- 

 osae as the true melanoides, and upon Tryon again for putting tnrgida down 

 as a synonym. 



' The uniformity in the size and proportions of this species would seem to 

 indicate that it is one of the older members of the Pleuroceridae, having 

 passed through the era of variability and plasticity and become suited to 

 a varying environment. That it is perhaps a vanishing race might be assumed 

 from the apparently narrow range and the smallness of its numbers. Its 

 competitor, plicata, is seemingly far more common and in numbers of individ- 

 uals exceeds it as in the Ohio River A. praerosa exceeds the small A. cos- 

 tata and possibly A. trilineata. 



The sculpture of melanoides is confined to fine growth lines which in 

 most specimens, not in all, are crossed by faint, discontinous revolving 

 lines. There are no nodules, tubercules or striae. Upon the adult specimens, 

 the only ones at hand, there occur no carinae. The rest scars are dark and 

 delicate. 



The body color varies from yellow to brown, with occasional specimens 

 of a greenish tinge. Yellow bandless forms are so smooth that they shine as 

 if varnished. The number of banded specimens is to unhanded individuals 

 as three to four. Only two banding arrangements were remarked — (i) band 

 at suture and at base; (2) band at suture, periphery and base. The ratio of 

 form 2 to form i is five to one. 



The columella forms an angle at its center rather than a curve, being 



