LEIOPTERTA OBTUSA. 21 



it. The long posterior wing, the tumid body, obsolete anterior end, and ribbed 

 surface are sufficient to define the species from others. 



LEioPTEiiiA om'LSA, M'Coj/, sp., 1844. Plate V, figs. 15—17. 



Lanistes obtusus, M-Coy, 1844. Sjnops. Carb. Foss. Ireland, p. 76, pi. xiii, fig. y. 

 MoDiOLA OBTUSA, Ethericlye, 1888. Brit. Foss., pt. 1, Palaeozoic, p. 285. 



Sjiecific Characters. — Shell small, triangularly ovate, gibbose, someAvhat oblique 

 and moderately inequilateral. The anterior end is small; the antero-posterior 

 angle j)ointed and projecting forwards slightly. The border passes downwards 

 and backwards in a curve, which is gradually extended till it passes round to meet 

 the posterior border, which is sinuously curved and emarginate. The hinge-line is 

 long and extended beyond the posterior margin, and straight. The umbones are 

 small, pointed, incurved, and placed a little in front of the middle line. The shell 

 is obliquely swollen from the umbones to the posterior inferior angle. In front of 

 this swelling is a well-marked oblique constriction, which notches the lower 

 border, more conspicuous in the right valve. The posterior slope is compressed, 

 and expanded into a small falciform ear. 



Interior. — Casts show the details of the hinge and interior to be normal. 

 E.derior. — The surface is very beautifully ornamented with several rather 

 close, raised, concentric ridges, carried up over the dorsal slope and ear to the 

 hinge-line; these are decussated by fine radiating lines, giving the shell a reti- 

 culated appearance. 



Dimensions. — PI. V, fig. 15, from (Uuniingham, Baidlaud, in the collection of 

 Mr. J. Smith, of Kilwinning, measures — 



Antero-posteriorly . . • .3 mm. 



Dorso-ventrally . . . .2-5 mm. 



From side to side .... 2*5 mm. 



Loralifies. — Scotland: Lower Limestone series of Cunningham, Baidland and 

 Law, Dairy ; Potmetal Plantation, Kirkcaldy, Fife. Ireland. 



Observations. — I have little hesitation in referring the shells in Mr. Smith's 

 collection and a series in the Museum of the Geological Survey of Scotland to 

 M'Coy's Lanistes ohtustis. The peculiarly beautiful marking of the shell is too 

 characteristic to mistake, in spite of the fact that I have been unable to find the 

 type specimen. M'Coy's description is very graphic, and accurately describes 

 Mr. Smith's shells. 



The shells from Dairy are very perfectly preserved, PI. V, figs. K) and 17. 



