SILURIAN MOLLUSCA. 188 



SO far as I can sec, with the H. obsoleta (Sow. sp.), but having an 

 apical angle of 30°, being thus exactly intermediate between it and 

 the H. conica (Sow. sp.), striking the eye as manifestly shorter 

 than the former, and more slender than the latter. Length 

 about 7 lines, width 3 lines, length of last whorl 2^ lines. 



Not uncommon in the state of casts in the Upper Ludlow rock 

 of High Thorns Underbarrow, Kendal, Westmoreland. 

 [Col. University of Cambridge.) 



Holopella monile (M'Coy). 



Sp. Char, Very slender, apical angle about 10°, spire of about 

 nine whorls (six preserved), each turn a little wider than long, 

 exceedingly convex, sutures deep, simple. Length 3^ lines, 

 width 1 line, length of last turn slightly less than 1 line. 

 The small size, extremely slender form, and very convex whork^ 



render it impossible to confound this with any other species. 

 Rare in the schists of Selattyn Road. 

 (Col. University of Cambridge.) 



Litorina undifera (M'Coy). 



Sp. Char. Turreted, broad, ovate ; spire pointed, about three- 

 fourths the length of the body- whorl ; apical angle about 80° ; 

 sutures channeled, having a little below them a thick spiral 

 ridge undulated by about eight vertical depressions, which 

 cross the whorls of the spire and upper part of the body-whorl ; 

 below this ridge is a wide concave space bounded by a second 

 thick undulating ridge, forming the most prominent part of the 

 whorl ; beneath this second ridge on the body-whorl are about 

 ten very delicate, subequal, spiral threads distinctly separated 

 by concave spaces, about two of which only are visible on the 

 turn of the spire ; entire surface crossed by very close, minute, 

 direct lines of growth. Length 3 lines, length of body-whorl 

 2 lines, width slightly more than 2 lines. 



This resembles some of the small oolitic Pleurotomarice, but 

 there is clearly no sinus in the lip, as indicated by the direct 

 lines of growth, and the shell is no doubt congeneric with the 

 L. carinata, from the young of which the undulations, &c. distin- 

 guish it. 



In the Aymestry limestone of Mortimer's Cross, Aymestry. 



{Col. University of Cambridge.) 



Loxonema elegans (M'Coy). 



Sp. Char. Spire very slender, elongate-conic, apical angle about 

 20° ', of about six elongate evenly convex volutions, crossed by 

 thread-like strise, arching forward at their ends, and with a 



