EAST AMERICAN SCAPHOPOD MOLLUSKS. 71 



DENTALIUM (GRAPTACME) AMALIENSE, new species. 



Plate 11, figs. 4, 5. 



A lot of nine excellent specimens in the National Museum collec- 

 tion at first I had considered to be a small race of Dentalium semis- 

 triolatum. The particular form of that species occurring in St. Thomas 

 is, however, rather larger and stouter than the average of specimens 

 from elsewhere. These specimens, on the contrary, are hardly more 

 than half the usual size of Guilding's species, and upon a critical 

 cQm]:)arison seem to lack certain characters necessary to link them 

 even subspecifically. The shell is moderately and regularly curved, 

 slender, regularly tapering, and has a round section. It is translu- 

 cent to transparent, white in color, with a polished shining surface. 

 It has no trace of the zigzag color bands. The sculpture consists of 

 exceedingly fine longitudinal, regularly spaced grooves, engraved 

 upon the posterior fourth or fifth of the shell, the sculpture disap- 

 pearing into a smooth, glassy surface. A long narrow apical slit 

 laterally placed is a feature that is not always observable even in 

 apparently perfect specimens. 



The measurements are: 



Length, 16 mm.; diameter, 1.5 mm. (type). 



Length, 17 mm.; diameter, 1.5 mm. 



The type. Cat. No. 250088, U.S.N.M., is from St. Thomas, taken 

 from a lot of nine specimens (Petit) . 



This species is distinguished from Dentalium, semistriolatum by the 

 relatively reduced space occupied by the sculptural features, by its 

 smaller size, and by the absence of any trace of zigzag color markings. 

 Its degree of curvature is also less. The lateral apical slit at once 

 separates it from D. ehoreum. Like D. semistriolatum it is probably 

 a littoral species of the Antillean region, but of very restricted range. 



DENTALIUM (GRAPTACME) SERICATUM Dall. 



Plate 12, figs. 1, 6. 



(?) 1834. Dentalium semistriolatum var. h. Guilding, Trans. Linn. Soc. London, 



vol. 17. 

 1881. Dentalium sericatum Dall, Bull. Mus. Comp. Zool., vol. 9, p. 37 

 1889. Dentalium sericatum Dall, Bull. Mus. Comp. Zool., vol. 18, p. 423, pi. 26, 



fig. L 

 1889. Dentalium sericatum BAhh, Bull. 37, U. S. Nat. Mus., p. 76, pi. 26, fig. 1. 

 1897. Dentalium (Graptacme) sericatum, Pilsbry and Sharp, Tryon's Man. 



Conch., vol. 17, p. 86, in part (not pi. 16, figs.), pi. 7, fig. 12. 

 1903. Dentalium sericatum Dall, Bull. 37, U. S. Nat. Mus., p. 76, pi. 26, fig. 1. 



This species in known by the type only. It is an immature shell, 

 answering to the description of Dental'.um semistriolatum except in 

 being more slender and more delicately marked, the zigzag color 

 zones of opaque white being especially bright and noticeable. It has 

 no apical notch or slit, I suspect this to be a race of Guilding's 



