226 



ON THE TOPOGRAPHY AXD (lEOLOCY 



T. p e r t e n II i s . Gabb, ii . s. 



Shell small, very slender, polished, whorls nmneroiis, nucleus large, vertical; surface of whorls flattened on the 

 sides and with comparatively large ribs ; base simjjle ; aperture small sub-quadrate. ' ■ 



Distinguished from both the preceding by its very slender form and more promi- 

 nent ribs. 



T. t u r r i t e 1 1 o i d e s . Gabb, n. s. 



Shell minute, slender, elongate, whorls about 14, the first placed vertically, the others regular, flat on the sides 

 and truncated above ; suture bordered by the top of the succeeding whorl ; base of body whorl sub-angulated on the 

 margin and rounded below ; aperture quadrate. Surface polished and marked by microscopic revolving lines. 

 Length .35 inch. 



This shell can be distinguished by its form which is exactly like that of a minute 

 Turritella. The sides of each volution are parallel, the top is tiiincated, and only 

 three or lour of the primary whorls show any convexity. - 



AXJRICULINA. Gray. 



A. a 1 1 a . Gabb, n. s. 



Shell slender, spire elevated, about three times as high as the mouth ; whorls six elongate, convex on the sides, 

 curving in abrujitly to the suture ; surface plain ; aperture sub-elliptical, lips simple. Length .1 inch. 



A little shell unlike any other in the formation. It can be at once recognized by 

 its few semi-flattened whorls and elongate apertui'e. , . . 



ACLIS. Loven. 



A. polita. Gabb, n. s. 



Shell minute, polished, subulate ; whorls seven, flattened on the sides ; suture channeled, sides of spire con- 

 vex ; base of body whorl elongate-convex, aperture small, acute behind, rounded in advance ; lips simple ; siirface 

 without ornament. Length .1 inch. 



In its polished surface and channeled suture, this shell is not unlike Oheh'scus 

 canaliculatus, but its short form, convex sides and simple rounded mouth will distin- 

 guish it at a glance. - : 



MENESTHO. MiiHer. ' i ] ^ . 



Pyramid, Couth., not Schum. Bolt., ct al. " 

 Monoptiigmn, H. and A. Ad., Shy., ct al. not I. Lea. , . ' 



Monotyijmu, Gray. , 



See note under I^IocJiel/i, with reference to the cinious misapprehension under 

 which most of the English authors have labored with reference to the true meaning 

 of Mr. Lea's genus. ■ • 



If we restrict the name Menestlio to these species without a columellar fold, as is 

 done by H. and A. Adams, then the ^fonoptygma Ad., &c. (not Lea), is without a 

 name. The present species has a fold, and I agree with the Adams' in making at 

 most ljut a sub-generic separation. ■ ' - ' 



M. clathrata. Gabb, n. s. 



Shell minute, elongate, spire high, whorls eight ; the first two polislied, the other six marked by regular longi- 

 tudinal and revolving elevated lines, sides of the whorls rounded, suture strongly marked. Aperture elongate oval, 

 sub-acute behind ; columellar fold strongly marked. 



