206 



ON THE TOPOGRAPHY ANT) GEOLOGY 



METULELLA. Gabh, n. gen. ; . ' : 



Shell fusiform, canal more or less produced ; inner lip covered with a thickened plate, continuous posteriorly 

 witli the outer lip. Interior of both inner and outer lips strongly denticulated or transversely sti'iated. Surface 

 cancellated or costate. . ' ' , • 



This genus is more distinctly fusiform than Metula, and has the additional char- 

 acter that the thickened inner lip is covered throughout its length by a series of 

 prominent denticles not corresponding with the covered-up surface ribs. 



M. venusta. Sby., sp. 



Golumhella mmista? Sby. Quart. Jour. Vol. VI. p. 46, pi. 0, fig. 6. 



The absence of all trace of a notch in the lip proves that Sowerby's reference of 

 this shell to Columbella was incorrect. Its fusiform shape, its canal, and the straight 

 lines of growth place it in i\\QFasinf£, and I have been obliged to institute the genus 

 to receive it and the following species. . _ 



M. fusiform is. Gabb, n. s. 



Shell fusiform, spire high, slender, a third longer than the mouth ; whorls nine to ten, ft)unded. Surface regu- 

 larly cancellate, except on the canal, by equal longitudinal and revolving ribs. On the canal the former are absent. 

 Aperture long and narrow ; canal produced, slightly recurved ; inner lix> covered by a thin callus posteriorly, thick- 

 ened in the middle, denticles as prominent as the external ribs and placed transversely. Outer lip thick witli an 

 acute margin with eight or ten teeth on the inner face. Length .7 inch, width .25 inch. 



J^ot common. ■ • 



TURMS. Bolt. " , . " . \ 



T. (Surcula) V i r g o. Lam., sp. _ _ , . ., , . , , 



Pleurotoma virgo, Lam. , _ ^' 



Turris mrgo, H. and A. Ad. Gen. Rec. Moll. 



Pleurotoma virgo, Moore. Quart. Jour. Geol. Soc. Vol. IX. pp. 12!J, 130. 



P. Haitcnsis. Sby. Id., Vol. VI. p. 50. . ' • 



P. Barretti, GupYiy. JcZ., Vol. XXIL, 290, pi. 17, fig. 6. . " " . ^ ... ' 



P. Jclskii, Crosse. Jour. Conch. 18C5, p. 34, pi. 1, fig. 8. . • _ . ' ' ( ' — 



p. AntiUarum, Crosse. (Kat. d'Orb.) Loc. cit. fig. G, 7. - - • ' - • 



A common shell, found living in the West Indies and on the coast of Mexico, and 

 one of the most abundant fossils throughout the Dominican beds, occurring over 

 their whole extent both stratigraphically and geographically. It varies very much 

 in the number, relative size, and arrangement of the ribs, although the general form 

 is quite constant. While Mr. Guppy's figure represents a not infrequent variety, 

 those of Mr. Crosse are not less characteristic. In some cases the ribs are all of the 

 same size, or they are alternate, or even have three or four fine thread-like lines in 

 the interspaces. In one specimen the whole surface is covered by large ribs only 

 sepai'ated by acute channels, from which form a regular gradation can be traced to 

 the other extreme, in which the body of the last whorl has ])ut one very prominent 

 ridge on the angle and but one or two below. The identity of all of these forms is 

 amply proven by a study of ovei* 500 specimens collected and a comparison with 



