360 Viscount cI'Archiac and M. de Verneuil's 



of the last volution, which is nearly sharp-edged, a narrow, scarcely distinct channel, limited beneath 

 by two threads, is recognized by its concave stria;. There are also other granular striae upon the 

 almost concave base of the shell. Umbilicus rather large. Aperture transverse, small, very de- 

 pressed. Right lip notched at its outer angle. Height, 5 millim.; diameter of the base, 12. 

 Villmar; rare. 



4. Pleurotomaria Defrancii, nob., Tab. nost., XXXII. f. 22, 22 a. 



Shell conoidal, pointed at the summit, with seven angular volutions, ornamented with two, irregu- 

 larly plicated transverse keels, the upper one simple and the lower double. Suture deep and canali- 

 culated. The stria of growth setting off from the suture turn abruptly backward to the second 

 keel composed of two contiguous lamellae, and beyond which these striae turn forward and then 

 run toward the base of the aperture. A third keel is seen at the base of the last volution upon the 

 prolongation of the suture, and a fine ridge placed below accompanies it to the right lip. Aperture 

 quadrangular. Columella salient, prolonged and slightly arcuated. Right lip furnished with a 

 linear fissure corresponding to the interval of the two lamellae of the second keel. Height, 14 millim. ; 

 diameter of the base, 10. 

 In some individuals the upper part of the volutions is decussated like the Pleurotomaria Orbignyana. 

 In others the keels are less elevated, and not so sharp, and the two folds of the second are more distant, 

 showing a shallow channel, as in the preceding species. 

 Villmar ; rare ; and Vise (Belgium), mountain limestone. 



5. Pleurotomaria undulata, Phill. Geol. of Yorksh., Part 2. PI. XV. f. 14. 



The snire of some individuals is only a little more elevated than in the shell of the mountain limestone 

 of BoUand. 



Slates of Wissenbach ; common. 



6. Pletirotomaria ? 



We have found at Paffrath, but very rarely, a small globular species with rounded volutions and which 

 has a rather broad raised band on the upper part of the volutions. It differs from the preceding in this 

 band, which is placed higher up ; and in the extremely delicate transverse striae which accompany it to 

 the base of the last volution. 



7. Pleurotomaria elegans, nob., Tab. nost., XXXIII. f. 3, 3 a, 3 6, 3 c. 



Shell sinistral, turbinated, composed of six regularly convex volutions. Suture simple, rather deep. 

 Volutions covered with very fine and close-set granular striae, eighteen to twenty in number, upon 

 the last volution. These granulations, which give to the surface of the shell the appearance of 

 shark's skin, are caused by the crossing of the transverse striae by oblique strise which run from the 

 suture to the base of each volution. Upon the last this base is bounded by a depressed, scarcely 

 evident band, of which the striae of growth are directed from front to back. The base of the shell 

 is grooved with concentric striae traversed by radiating and undulating lines of growth, but without 

 producing the elegant granulations that are seen on the volutions. Aperture depressed, elliptical. Co- 

 lumella salient, a little arched. Slit rather wide, but not deep, placed at the lower angle of the right 

 lip and corresponding to the external band. Height, 13 millim,; diameter of the base, the same. 



In this species, remarkable for its sinistral volutions, there are individuals in which the rows of granu- 

 lations arc of two sorts, some composed of united and contiguous grains alternating with others whose 

 grains arc distinct and isolated, and of a rhomboidal form ; as is seen in the magnified fragment at fig. 3 c. 



Villmar; common. 



