484 Systematic Paleontology 



well-preserved specimens longitudinally marked by filiform undulating 

 striae. The spire appears to be depressed often when the shell retains its 

 natural proportions, and at other times from pressure ; in a few examples 

 it is considerably elevated. The fine undulating longitudinal striae do not 

 always appear, and sometimes only upon a portion of the surface, even 

 when there is no appearance of abrasion. In other examples they have 

 evidently been worn off, leaving the transverse striae well preserved." 

 Hall, 1852. 



Length 1.8 cm.; diameter 1.9 cm. 



Occurrence. — Heldeeberg Foematiox, Keyser Member. Viaduct 

 Cumberland. 



Collection. — U. S. National Museum. 



[Maynard.] 



Order OPISTHOBRANCHI ATA 



Suborder CONULARIDA 

 Family TENTACULIDAE 



Genus TENTACULITES Schlotheim 



Textaculites ? acus Clarke 



Plate LXXXYII, Fig. 5 



Tentaculites ? acus Clarke, 1900, Mem. N. Y. State Mus., No. 3, vol. iii, p. 28, 

 pi. iii, figs. 1-7. 



Description. — " Shells having as large size as those of T. elongatus but 

 with the exterior surface smooth or with very faint, distant, broad, con- 

 centric depressions and fine, indistinct and somewhat irregular growth 

 striae. The internal cast is similar to that of 2\ elongatus, but has the 

 constrictions less deep. Specimens of this species are not uncommon. The 

 wall of this species is thick and cellular, and a transverse section gives 

 two or more concentric circles at any plane, showing the ensheathment 

 of the funnel-like divisions of the interior. This structure is much more 

 pronounced than in any species of Tentaculites observed by the writer 

 and, though more regular than in Cornulites, may prove to be of the same 

 nature.-' Clarke, 1900. 



