226 MISS J. DONALD ON THE GENUS [May 1895, 



of two whorls. The upper part of the spire is worn, so that it is 

 impossible to say when the ornamenting keels commenced. Length 

 = 10 millim. ; width =3 millim. 



There is another individual in the collection of Dr. John Young 

 (PI. VIII. fig. 10), consisting of the same number of whorls ; the 

 apex is broken, and its length is 9 millim., width 2h millim. 



Locality. Law, Dairy. 



Formation. Lower Limestone Series (d 3 ). 



Section Hypeegonia, Don. 



Mttechisonia (Hypeegonia) deplanata, sp. nov. (PI. IX. figs. 8, 10.) 



Shell elongated, turriculated, upper part of the spire sometimes 

 slightly convex in outline, composed of more than twelve whorls. 

 Whorls increasing gradually, angular below the middle, flattened 

 both above and below the angle. Ornamented by a strong keel on 

 the angle, another at a distance below, appearing just above the 

 suture on the upper whorls, and one or two very fine lines on the 

 body-whorl below this keel. Above the angle there are two finer 

 keels with a wide space between the lower one and the angle, which 

 probably represents the position of the sinus. Lines of growth 

 strong and distinct, curving backwards above over the two finer 

 keels and forwards below the angle, invisible on the wide space 

 above. Base flattened. Mouth but slightly longer than wide. 

 Columella simple. No umbilicus. 



This shell strongly resembles M. quadricarinata, M'Coy, 1 and 

 M. quinquecarinata, De Kon., 2 but may be distinguished by having 

 only one keel instead of two below the angle, and that at a consider- 

 able distance ; moreover the base is much flatter. 



Dr. John Young possesses one specimen (PL IX. fig. 8). It 

 consists of eleven and a half whorls ; the apex is broken ; if entire 

 there would be one or two whorls more. I have also two fragments 

 which were given me by Dr. Young. Length = 6| millim. ; width 

 = 2 millim. ; height of body- whorl =2 millim. 



The . Armstrong Collection in the Museum of Science and Art, 

 Edinburgh, contains portions of the spires of two individuals. The 

 apex (PL IX. fig. 10) of one of these is well preserved: it is 

 somewhat blunt; the nucleus is simply coiled and consists of two or 

 three smooth whorls. Mr. Thomson has a single specimen in his 

 collection, of which only five whorls are preserved, the apex being 

 broken. 



Locality. Glencart, Dairy. 



Formation. Upper Limestone Series (cZ 3 ). 



I have also one small specimen given me by Dr. Young from the 

 Lower Limestone Series of Law, Dairy. 



1 ' Syn. of the Cbar. of the Carb. Limest. Foss. of Ireland,' 1844, p. 42, pi. v. 

 fig. 9. 



2 Ann. Mus. Boy. Hist. Nat. Belgique, 'Faune du Calc. Carb. de la Belgique,' 

 vol. viii. (1883) pt. iv. p. 23, pi. xxxiv. figs. 14-16. 



