DENTALlUM-LiEVIDENTALIUM. 97 



Very peculiar in the anal plug and slit which are formed as in 

 D. calamus, a species differing only in being striated throughout. 

 The sculpture is characteristic of a small group of species comprising 

 the above named forms and the D. semistrlatum group, which though 

 varying greatly in the details of the anal slit, we hold to be closely 

 allied. 

 D. CALAMUS Ball. PI. 17, figs. 55, 56, 57, 58, 59. 



Shell very slender, slightly arched, white, translucent, the soft 

 parts showing through the shell ; finely longitudinally grooved 

 [throughout, or for the greater part of the length], the grooves uni- 

 form, the interspaces flat and slightly wider anteriorly ; aperture 

 hardly oblique, anal end apparently trimmed off obliquely fo7- a short 

 distance on the convex side, glandiform, phallic, vertically narroioly slit, 

 the slit longer on the convex side, the "glans"-like portion smooth, 

 polished, usually with a little ledge around it. Length of shell, 

 19*5; height of arch from chord, 2'25 ; diameter of aperture, 1'25 ; 

 of anal end behind the "glans," 0'8 mill. Grooves in the middle 

 part of the shell about sixteen to the millimeter of circumference. 

 {Ball). 



Turtle Harbor, Florida, in 4 fms. ; and Cape Fear (Dr. W. H. 

 Rush, U. S. N.) ; Pliocene of the Caloosahatchie, Florida. 



D. calamus Dall, Blake Rep., Bull. M. C. Z., xviii, p. 421 (1889) ; 

 Bull. U. S. Nat. Mus., no. 37, p. 76 ; Trans. Wagner Institute, iii, 

 p. 440. 



D. calamus differs from the very closely allied D. sectum in being 

 striate for nearly or quite its entire length, while the other is smooth 

 toward the aperture. Very young specimens of calamus have the 

 slit much more open, and the form tapering. D. calamus attains a 

 length of 26, diam. of aperture 1*7, of apex 1*3 mill. Figs. 58, 59 are 

 drawn from a Florida specimen in which the anterior portion of the 

 tube is smooth for a short distance ; figs. 55-57 are from a specimen 

 taken off Cape Fear, striate throughout. The name is doubly appro- 

 priate. 



Subgenus L^videntalium Cossmann, 1888 (s. lat.). 



Lmvidentalium CossM., Ann, de la Soc. Roy. Malacologique de 

 Belgique, xxiii, p. 9. Type D. incertum Desh. 



Shell of moderate or large size, smooth, with growth lines only 

 circular or slightly oval in section ; apex simple (typically), or with 

 a short notch on the convex side as in Antalis. Type D. incertum. 

 7 



