[NVERTEBRATE PALEONTOLOGY. 



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Fia ii. 



Fig. 4-2. 



Odontobasis constvicta. 



rather impressed; aperture narrow-sub.oval, a Little oblique, obtusely angular 

 above, and tapering below; columella typical, meeting the body-volution 

 above, at the upper termination of the revolving sulcus, at a very obtuse, 



undefined angle; entire surface marked by moderately 



distinct, irregular lines of growth, crossed by numer- 

 ous little flattened revolving, bands, or lines, wider 

 than the furrows between, excepting on the upper 

 constricted part of the body-volution, where they are 

 smaller and about equal the furrows. 



Length, 0.38 inch; breadth, 0.'2'2 inch; slopes of 



v > ma %- spire slightly convex, and diverging at an angle of 



iiilicd ','i diameters. ' ° J 



Fig. 42. Ad opposite view of about 54°. 

 same, showing aperture, . 



& c . 1 he constriction around the upper side ot the 



body-volution is moderately well marked, particularly near the aperture; and 

 as the vertical folds are most prominent around the outer edge of this con- 

 stricted part, and show a little tendency to terminate there, they give the 

 body-turn a slightly shouldered appearance. Of the smaller revolving lines 

 on the upper constricted part, there are three or four, the upper one of 

 which is only very faintly separated from a little wider, somewhat thickened, 

 space above, that gives a slightly banded appearance to the suture. 



I am not positively sure that this shell is specifically identical, in all 

 respects, with the type of F. constrictus, Hall and Meek. In the constricted 

 and almost shouldered appearance of the upper part of its body-volution, as 

 well as in the less straightened outline of its columella, and the consecpient 

 slightly different form of its aperture, it would seem to present well-marked 

 differences. The fact, however, that the type of /•'. constrictus is much smaller 

 than our specimen (being only about 0.20 inch in length, and almost certainly 

 a young example), while the constriction mentioned seems to be only well 

 defined on the body-volution of our shell, renders it very probable that the 

 small size and the imperfect condition of the type of F. constrictus prevented 

 the exact outline and the obscure plaits of its columella from being seen.* 

 Consequently, as it agrees very closely in form and proportions, as well as in 

 surface-ornamentation, and the peculiar revolving sulcus at the connection of 

 the beak with the swell of the body- volution, I can scarcely doubt its identity. 

 Should a direct comparison, however, show these shells to belong to distinct 



* These little plaits were also overlooked by the engraverin cutting the above figure showing the 

 aperture. 



45 H 



