262 CARBONIFEROUS LIMESTONE FOSSILS. 



body-whorl y^^^, width of body-whorl yYoj width of penul- 

 timate whorl -^^Q, space between last and penultimate sutures 

 TWUf width of mouth -f^^j. 



This beautiful species is so totally distinct in form from any of 

 those described that it is unnecessary to compare them. The 

 very abrupt attenuation of the elongate spire gives so much the 

 outline commonly seen in Limnaa as to suggest the specific 

 name : in addition to this remarkable peculiarity, the species 

 differs from its congeners in the conoidal attenuation of the pro- 

 duced fronts from the hne of greatest width of body-whorl, which 

 is at about one-third its length below the suture. 



Not very uncommon in the carboniferous limestone of Lowick, 

 Northumberland. 



{Col. University of Cambridge.) 



Macrochilus bi^evispiratus (M'Coy). 



Desc. Elliptical, moderately gibbous, most so about the middle of 

 the length; spire about one-fourth of the total length, pointed, 

 of four whorls gently convex in the middle ; sutures slightly 

 imbricating; apical angle varying from 82° to 100°; anterior 

 portion or base produced, moderately convex ; surface smooth, 

 with very faint fine striae of growth visible near the mouth, 

 being scarcely sinuous and very slightly oblique ; mouth elon- 

 gate ovate, indented by the posterior part of the body-whorl ; 

 anterior half of columella thickened, arched. Length of rather 

 small specimen 9 lines, proportional length of mouth or last 

 whorl y^Q^Q, width of body-whorl y^^^^, width of mouth y^^, 

 space between last and penultimate sutures y^^. 



The extreme shortness of the spire separates this form from 

 all of the genus at once, except the M. Michotianus (DeKon.) ; 

 from that globose species, it is distinguished by its much more 

 elongate slender form (indicated by the much less proportional 

 width of the body-whorl when compared with the total length), 

 fewer spiral whorls, less convexity, and the whorls sloping gra- 

 dually to the sutures. 



Eare both in the lower carboniferous limestone of Derbyshire, 

 and in the carboniferous limestone of Lowick, Northumberland. 



[Col. University of Cambridge.) 



Straparolltis costellatus (M^Coy). 



Desc. Discoidal, depressed, very obtusely conic ; spire of rather 

 more than six very gradually increasing whorls, each slightly 

 convex above, strongly indenting the suture, which is an im- 

 pressed sharp line ; apical angle 110° (from the obtuseness of 



