TURBINACEA. MOLLUSCA. ODOSTOMIA.. 273 



with no obvious characteristics, from description only, I must leave it 

 unsettled. 



It is almost certainly the Turritella hisuturulis of Say ; at least, I 

 know of no other shell which will at all answer to his description. 

 The figure and description of Rissoa ruj^estris, Forbes, also cor- 

 respond with it. 



Odostomia seminu'da. 



Shell acute-conic, white, with coarse revolving lines, crossed on 

 the upper lohorls^ and on the upper half of the lower whorl, by lon- 

 gitudinal lines. 



Figure 178. 



State Coll., No. 30. Soc. Cab., No. 2418. 



Jannnia seminuda, Adams ; Bost. Journ. Nat. Hist., ii. 280, pi. 4, f. 13. 



Shell acute-conic, glossy white, translucent ; whorls six or 

 seven, convex, the upper ones and one half the lower whorl with 

 numerous ridges or folds, crossed by three, equidistant revolving 

 lines, giving the surface a granulated appearance ; at the base of 

 the lower whorl are four more revolving lines, beginning on the 

 middle where the folds terminate abruptly ; suture distinct, divid- 

 ed by an indistinct spiral ridge ; aperture oval, one third the 

 length of the shell ; the outer lip very thin, and scolloped by the 

 revolving lines ; the base is prolonged into a concave angle, and, 

 rising, revolves within the shell, forming a single inconspicuous 

 fold on the pillar. Length J-?o- inch, breadth jl^ inch, divergence 

 30°. 



First found by Professor Adams, at Dartmouth, on valves of 

 Fecten concentricus, taken up beyond low-water mark. 



This shell is readily distinguished from all others found in our 

 waters of a similar size and outline, by the sculpture of the lower 

 whorl, the upper half of which is granulated by the decussating lines, 

 and the lower half marked by revolving lines only. It is smaller, and 

 less elevated proportionally than O. trifidns. Making allowance for 

 variations in magnifying two shells so small, this seems not to differ 

 much from Turbo spiralis of Montagu, ( Test. Brit. 323, pi. 12, f. 9). 

 He neither represents nor describes any revolving lines crossing the 

 folds. These he may have overlooked ; for Fleming distinctly men- 

 tions them. 



35 



