154 GASTEROPODA OF THE INFERIOR OOLITE. 



71. Cerithium subabbreviatum, D'Orb., 1850. Plate VIII, fig. 11. 



1850. Cerithium subabbreviatum, D'Orb. Prod., vol. i, p. 271. 

 1842. Melania abbreviata, Desl. Mem. Soc. Linn. Norm., p. 219, pi. xi, 



fig. 67. 



Bibliography, Sfc. — The most natural course, in this case, would be to retain the 

 specific name given by Deslongchamps,by whom the species was originally described. 

 But the specific term abbreviatum has already been bespoken by Mr. Leckenby 

 for a Cerithium described by him. 

 Description : 



Length . . . . .16 mm. 



Width . . . . .6 mm. 



Ratio of body-whorl to entire shell . . 35 : 100. 



Spiral angle . . . .28°. 



Shell ovate, turrited. Spiral angle scarcely if at all convex. Number of whorls 

 about twelve ; these are narrow and subtumid ; suture close and but little inclined. 

 The spiral lines are very fine and numerous, and extend over the entire shell (in 

 the figured specimen the faintness of this ornament is in part due to wear). The 

 longitudinals are extremely numerous, extending with regularity, in the form of 

 slightly arcuate costse, from suture to suture. 



Body-whorl subventricose. Aperture ovate with a considerable callus on the 

 columella ; canal short, small, and slightly refiexed. 



Relations and Distribution. — Deslongchamps pointed out the relationship of this 

 rare shell to " Melania scalariformis." The shortness of the whorls of the spire 

 and the ventricose character of the body-whorl constitute its principal difference. 

 A single specimen from P 1? Burton Bradstock. 



72. (?) Cerithium obesdm, sp. nov. Plate VIII, fig. 12. 



Description : 



Length . . . .8 mm. 



Width . . . . .5 mm. 



Ratio of body-whorl to entire shell, about . 50 : 100. 



Spiral angle, about . . . 50°. 



Shell short, ovate, turrited. Number of whorls about six, convex, and increasing 

 very rapidly. The ornaments consist of three or four spirals which decussate with 



