NO. 1-183. 



I m COP TID MOLL USKS—BA R TSCII. 



139 



Measurements of Holospira {Bostrichocerdrum) hidalgoensis. 



a Type. 



HOLOSPIRA (BOSTRICHOCENTRUM) TAMAULIPENSIS, new series. 



Plate IV, tig. 2. 



Shell elongate-conic, horn-colored, with strong white riblets. Nuclear 

 whorls two, light ^^ellow-horn-color, very minutely granulose. Ter- 

 minal cone long and gently tapering, having the whorls mo<:lerately 

 well rounded. Cylindrical portion of the spire consisting of the last 

 three or four volutions. All the whorls are strongly and quite regu- 

 larly ribl)ed. The ribs are slender, somewhat compressed laterally, 

 forming low lamellae, about one-fourth as wide as the spaces which 

 separate them. In the type there are 40 upon the second ribbed 

 (i. e., the fourth) whorl, 56 upon the ninth, and 5-4 upon the penulti- 

 mate volution. Sutures well impressed. Last whorl somewhat elon- 

 gated and narrowed basally. Periphery slightly angulated. Base 

 well rounded, marked by the rather crowded continuations of the ribs, 

 which extend strongl}" into the umbilical rimation. Last whorl shortly 

 free behind the aperture; the free portion is marked by strongly 

 lamellar riblets, which become decidedly crowded and weaker behind 

 the peristome. The free portion of the parietal wall is decidedly pinched 

 a little to the left of its junction with the outer wall, which lends it a 

 somewhat sinuous outline. It is marked by the continuation of the 

 riblets of the outer wall. Aperture oblique, semioval, the short diam- 

 eter of the oval being represented by the parietal wall. Peristome 

 quite strongly expanded but not reflected, Avhite. Internal pillar 

 slender, hollow throughout, marked l)y an obsolete submedian twist, 

 which gives place to a weak, short fold in the penultimate whorl. This 

 fold extends only over about half a turn and almost rests upon the 

 floor. There are 32 specimens of this species in the collection of the 

 U. S. National Museum, Cat. No. 187979, collected by E. W. Nelson 

 and E. A. Goldman at Camargo, Tamaulipas, Mexico. 



