104 SYSTEMATIC ARRANGEMENT 



oblong ; inner lip thick, callous behind ; outer simple, acute. Oper- 

 culum half-ovate, subspiral; apex curved. — Adams, Gen, Moll. 

 t. 32. f. 8. 

 1. M. costata. 



Foot broad, truncate, ovate. Head proboscidiform. Tentacles 

 setaceous. Eyes exterior, basal. Tongue linear, ribbon-like ; apex 

 at each side membranaceous. Teeth in seven series ; central and 

 inner lateral fixed ; outer lateral versatile ; central transverse, sub- 

 quadrate, five-hooked ; central hook very large ; the first lateral hook 

 bipartite, rather six-hooked ; the second hook the longest ; the two 

 or three lateral teeth subequal, with three hooks in front. Opercu- 

 lum horny, half-ovate ; apex subspiral. — Rossmasler, Icon. iii. t. 68. 

 f. 836. 



Central tooth of Melanopsis buccinoides transverse, subquadrate, 

 somewhat prominent at the base in the middle, cutting edge trans- 

 Fig. 54. — Teeth of Melanopsis buccinoides. 



verse, with five pointed lobes ; lateral teeth strong, first thick, with 

 a short projecting process on the inside, the base produced on the 

 outside, the upper margin unequally lobo-dentate, the second and 

 third slender, somewhat similar, arcuate, impressed and thickened 

 in the middle, the tip recurved and three-toothed (fig. 54). 



11. Clionella. 

 Shell fusiform, plicate ; whorls with a compressed groove in front ; 

 mouth ovate ; outer lip with a deep posterior sinus. Operculum 

 half-ovate ; apex subspiral. — Adams, Gen. Moll. t. 32. f. 10 a, b. 



1 . C. sinuata. Pleurotoma buccinoidea, Quoy, t. 90. f. 5 ; Adams, 

 Gen. Moll. t. 32. f. 10. 



e. Aperture of shell with a straight canal in front. 



12. Io. 



Shell fusiform ; whorls angular, tubercular ; mouth ovate, large, 

 dilated in front ; canal rather produced ; outer lip simple. Oper- 

 culum ovate ; whorls three or four, very rapidly enlarging. — Adams, 

 Gen. Moll. t. 31. f. 8. 



1. I. fluviatilis. 



