122 K. J. Bush — Marine Gastropods referred to 



VITRINELLIDiE. 



Cyclostrematidae auth., in part and Adeorbidae Dall, in part. 



Vitrinella C. B. Adams, 1850. See page 105. 



Type, Vitrinella helicoidea 0. B. Adams. 



Vitrinella helicoidea C. B. Adams, Monograph of Yitriuella, p. 9, 1850. non Tryon, 

 Manual, x, pi. 34, figs. 40, 41, 1888. 



Plate XXIII. figs. 9, 9a. 



" Discoidal : white, opaque and translucent in transverse alternat- 

 ing lines : with a single impressed spiral line near the summit of the 

 whorls, and very fine irregular transverse striae ; apex very obtuse ; 

 spire slightly and convexl}^ elevated ; whorls four, moderately con- 

 vex, rapidly increasing with a lightly impressed suture ; last whorl 

 regularly rounded, a little compressed beneath. Aperture not modi- 

 fied by the last whorl ; labium with a rather thick deposit ; umbili- 

 cus large and deep, with a spiral carina, exhibiting all the whorls. 

 Mean divergence about 150° ; length of spire '01 inch ; total length 

 •03 inch ; greatest breadth -075 inch ; least breadth '06 inch." 



A specimen from station 2280, off Cape Hatteras, N. C, in 16 

 fathoms, agrees so closely with Adams' description that I have ven- 

 tured to figure it as an example of this, the type species of Vitrinella. 



It is a small, semi-transparent, smooth, shining shell of about 

 three and one-half convex whorls, forming a very low spire with 

 obtuse apex and large body-whorl. Suture inconspicuous with an 

 internal spiral line just below it showing through the shell. Umbili- 

 cus moderate, deep, showing all the whorls, with straight walls, dis- 

 tinctly angulated and defined on its outer margin by a rather small, 

 rounded thread. Aperture oblique, nearh' circular. Peritreme 

 simple with a thin sharp edge, becoming thickened and rounded 

 along the columellar margin and modified on the body- whorl into an 

 inconspicuous, irregular, very thin glaze. 



In a basal view the aperture is decidedly angulated below, the lip 

 curving forward from the body-whorl, then backward and abrujJtly 

 inward to join the sinuous pillar-lijD. 



Under the microscope the surface is marked by very delicate sinu- 

 ous raised lines in the direction of the lines of growth. 



Greatest width, about 2-3'""^; height about 1"^"\ 



The higher spire and angulated and carinated umbilicus distin- 

 guish this species from V. helicoidea as figured by Tryon. 



