44 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 59. 



margin smooth and sharp; operculum tack-shaped with a three- 

 cornered spick or tooth situated on the edge of the tack head or 

 basal circular plate; anterior surface of basal plate concave marked 

 with a few fine lines radiating from the center and a few irregular 

 concentric lines; posterior side of the basal plate and the sides of 

 the three-cornered tooth or apophyse marked by irregularly ramify- 

 ing and deeply impressed grooves or sulci which probably represent 

 the seats of muscular or ligamental attachments ; posterior extremity 

 of the tooth pointed and tripartate; operculum in place is entirely 

 behind the anterior margin of the aperture, thus forming a water- 

 tight stopper for the tube. 



This species is one of the commonest fossils in the Ripley forma- 

 tion at Coon Creek. It is represented in the collections from that 

 locality by hundreds of specimens, several dozen of which retain the 

 operculum in place. A few immature forms have been found at- 

 tached, but none of the specimens preserve the complete nucleus. 

 This is broken away from all the specimens examined, leaving the 

 apices perforate. This species is somewhat similar to the species 

 Hamulus jonahensis (Cragin) 12 from the Austin Chalk of Texas, but 

 does not possess the vigorous incremental sculpture that character- 

 izes the tubes of the Texas species. The species Serpula scxsulcata 

 Miinster, 13 a species of Hamulus, from the Upper Cretaceous of Ger- 

 many, has six axial ribs on the tube, but most commonly the Euro- 

 pean species of this genus are characterized by seven ribs instead 

 of six. Two of these are : 



Dentalium deformis d'Orbigny u (pi. 9, figs. 7, 8) from the Ceno- 

 manian, Le Mans, France ; and Serpula septem sulcata Reich and Cotta 15 

 (pi. 2, fig. 10) widely distributed in the Cenomanian of Saxony and 

 especially abundant in the Serpulitensand of Bannewitz near Dres- 

 den. The Ripley species Hamulus major Gabb 16 from Eufaula, 

 Alabama, has only three or four low axial costae on its tubes which 

 are less regular and symmetrical than the type species of this genus. 

 The Oxfordian species Serpula vertebralis Sowerby, 17 a Jurassic species 

 found in both England and in France, has only four axial ribs, but 

 in many respects it resembles Hamulus onyx Morton and should be 

 included in the genus Hamulus. 



Occurrence. — Ripley Formation. Dave Weeks place on Coon 

 Creek, McNairy County, Tennessee. 



Collections. — -Philadelphia Academy of Natural Sciences. Johns 

 Hopkins University. Vanderbilt University. U. S. National 

 Museum (Cat. No. 32460). 



" Cragin, F. W., Fourth Ann. Rept. Geol. Survey or Texas, 1893, pi. 29, figs. 12-14, Austin. 

 i> Go!d/uss, Petrefacta Gormaniae, vol. 1, p. 238, pi. 70, fig. 13. 



11 Geinitz, H. B., Grundriss dor Versteinerungskunde, p. 252, pi. 16, fig. 18a, 6, c. Dresden, 1842. 

 i* Wanderer, K., Tierversteincrungen aus der Krcide Sachsens, 1909, p. 21, pi. 3, fig. 12, Jena. 

 i« Gabb, W. M., Journ. Acad. Nat. Sci. Phila., 1850, p. 399, pi. 68, fig. 46. 



" Sowerby, Mineral Conehology, pi. 599, figs. 6-9. Bronn, H. G., Lethaea Geognosfiea, vol. 0, p. 415, 

 pi. 27, fig. 5a, 6. Stuttgart, 1852. 



