260 PROCEEDINGS OF THE ACADEMY OF [1893. 



Soft parts : the foot is about as long as the diameter of the shell, 

 quite transparent, a little more so than in V. pulchella and excen- 

 triea. The jaw, PI. VIII, fig. N, is rather strongly curved moder- 

 ately high, stout, chestnut colored in the inferior part, with 16-18 

 rather strong ribs on the front side, leaving about i of either side at 

 the end ribless and smooth. The cutting edge is denticulated, and 

 sometimes appears a little more straight in the median part, but 

 there is no projection. The lines of growth are distinctly visible. 

 Width of jaw 0-25, height 0-088 mm. 



The radula has 69-72 transverse rows of 27 (or 29) teeth. In 

 the central the side cusps are very small, barely perceptible, and 

 the side margins of the plate are curved up in nearly their entire 

 length. There are 4 perfect laterals with the mesodont compara- 

 tively thin, the ectodont very small, scarcely half the size of the 

 same in V. excentrica. The fifth makes the transition, but resembles 

 rather the laterals, having a well-formed plate of attachment with a 

 projecting posterior distal angle. Its mesodont shows an indication 

 of its transformation and the ectodont is essentially simple, but, at 

 least in some parts, with two points. The sixth or first marginal is 

 somewhat triangular, and with a distinctly backward extended plate 

 of attachment, and the reflection with 2 or 3 short distal cusps, as it 

 is still in the following or seventh tooth. On the other marginals 

 the cusps are comparatively small and stand immediately up on the 

 bases. Length of the radula 0*71, width 0-22-023 mm. 



V. costata is distributed over a wide geographical area, being 

 found all over Europe, Northern Africa, and the most part of Asia. 

 In North America it seems to occupy a wide area also, though it is 

 not as common as V. pulchella. It has been cited from Philadelphia 

 and Cincinnati. I have seen it from Washington, D. C, from 

 Quebec, Canada, and Isle d'Orleans, near that city, collected by 

 Mr. A. W. Hanham, also from Iowa, Nebraska, Kansas and Colo- 

 rado. All reports of distribution must be received with reserve, 

 and especially those from high altitudes in western North America, 

 as under the name of costata doubtless different forms are com- 

 prised, such as gracilicosta, parvula, cyclop h or el la and others. It 

 has also been found in Australia, by Cox, as reported by Brazier 

 (Journ. Conch., 1879).* 



Until recently, and even now, V. costata has been considered a 

 variety of pulchella. The characters of the shell, decidedly and 



* See Appendix. 



