G78 Systematic Paleoxtology — Uppeu Devonian 



It does not seein desirable to erect a new genus for the reception of the 

 shells described based upon the materials observed. They are hence 

 referred tentatively to the genus Loxonema. 



Occurrence.' — Jennings Formation, Chemung Member. Oakland- 

 Altamont Eoad ; 2 miles north of moi;th of Town Creek, 1949. Park- 

 head Member. Williams Eoad, on Polish Mountain, 1352, IGGO abun- 

 dant: 2 miles north of mouth of Town Creek, 1723, 1842 common; 2 miles 

 west of Pawpaw, 1493: Little Orleans, abundant; Fifteenmile Creek, 1 

 mile above Little Orleans, 1773; 21/) miles above mouth of Sideling Hill 

 Creek. 



Collection. — Maryland Ceological Survey. 



Superfamily TAENIOGLOSSA 

 Family PURPURINIDAE 



Genus TRACHYDOMIA Meek and Worthen 



Traciiydomia pr.ecursor (Clarke) 



Plate LXIX, Figs. 15, 16 



Palaotrochus pracursor Clarke, 1885, Bull. U. S. Geol. Surv., No. 16, p. 55, 

 pi. iii, figs. 6-9. 



Description. — Shell rotund, with short spiral, and broad body whorl. 

 Volutions 5-G. Sutures deeply impressed. Apical angle 50°. Body 

 whorl narrowly flattened at the suture, thence the slope being broad de- 

 pressed curve to the greafest diameter which is % the distance across the 

 whorl. Aperture entire, oval, embracing i/^ of the penultimate volution. 

 Outer lip thin, uninterrupted. Inner lip somewliat thickened: excavate. 

 Shell non-uiubilicate. 



Surface with revolving rows of subeijual tubercles, those adjoining the 

 suture, and at the periplier}', being the more prominent. Xiiie or ten of 

 these rows occur on the body whorl. Yeiy fine concentric lines cross 

 this tulicrcled surface, and these are more noticeable upon the earlier 

 whorls. 



Height 10 mm.; diameter 7 mm. 



