CERITHIUM GRACILENS. 37 



1 am satisfied that the Lebanon specimens before mc belong to a species 

 distinct from that. In the first place, they are proportionally longer and 

 narrower than Michelin's species, which has a spiral angle as great as 30° and 

 32°; while the spiral angle of the shells in hand is never larger than 16°. 

 Again, according to the best description of trimonile, that of Stoliczka, the 

 tubercles of the uppermost or posterior row in young specimens are always 

 distinctly divided by a deep groove, while the tubercles in the other two rows 

 approach so near each other that they seem to form short transverse ribs. 

 The anterior row has generally the largest tubercles; but sometimes the 

 tubercles of the two anterior rows are nearly equal, and not so strong as 

 those of the posterior row. Besides the tuberculated ridges, the entire 

 shell-surface is minutely striated. None of the foregoing specifications of 

 Stoliczka's apply to the present species. The younger specimens have the 

 tubercles of the anterior and posterior rows equal in size; but in some of 

 the older, the tubercles of the posterior row become the larger. Nor are 

 the tubercles of either row divided by a groove. The central row always 

 consists of smaller tubercles, much less prominent and distinct than those of 

 the other rows. On the base of the last or anterior whorl is a single row 

 of indistinct tubercles parallel to the other rows. Old specimens show heavy 

 lines of growth upon the sides and base. Coll. Thomson. 



Locality and Position. — Probably Abeih or its vicinity. The specimens 

 of this species, like those of Nerinea gemmifera, already noticed on page 26, 

 are completely silicified and colored reddish or yellowish by oxide of iron. 

 Fraas represents a splintery limestone bed (splitterige Kalkbank) of the Gas- 

 teropod zone of Abeih as being most productive of Cerithia. Since in lime- 

 stones the mineralizing factor of fossils is more commonly silex, it is highly 

 probable that these specimens were taken from the limestone layer of the 

 Turonian Gasteropod zone. 



UNDETERMINED. 



Six casts from the Merrill collection, of which the two in best condition 

 are represented on Plate II by figures 'J a, h. They seem to be identical 

 with the specimen described and figured by Conrad (Official Report, p. 234, 

 App.. PI. v, fig. 43) as CancelUria petrosa. The casts have a few distant and 

 rather oblique longitudinal ribs, but 1 find no proof that they belong to the 

 genus Cancellaria. 



