384 



yEW TBIASSIC UNIOS FROM TEXAS- SIMPSON. 



VOL. xvm. 



Locality. — Five miles iiortlieast of Dockiim, bead of Duck Creek, 

 Dickeus County. Five j)airs, more or less perfect, were sent irom a 



gray sandstone near Dockum, and 

 what are probably tliree or four 

 heavily incrusted valves of tlie same, 

 from clayey conglomerate from Duck 

 Creek. They recall quite strongly 

 young specimens of Z^nio dignatus 

 from Assyria, and U. pictorum and 

 tlie allied simple forms of Europe. 



Fig. 3. 



UNIO DUMBLEI, NEW SPECIES. 



Fig. 4. 



UNIO GRACILIRATUS, NEW SPECIES. 



UNIO GRACILIRATUS, new species. 



Shell small, oblong oval, rounded before and slightly biangular 

 behind; dorsal region more curved than the base; growth lines mod- 

 erate; surface generally, but especially the posterior region, more or 

 or less sculptured with delicate, somewhat broken, and wavy narrow 

 lin^. Length, 40 mm.; height, 23 mm.; diameter, 16 mm. 



Xoc«?/7i/.— South of spur. Headquarters 21, Dickens County, Texas; 

 head of Duck Creek, Dickens County. 

 Four left valves in a limestone matrix 

 were sent from the former locality, 

 and two left valves embedded in 

 coarse granulated limestone from the 

 latter. One right valve of what is 

 probably this species was sent from 

 the Dockum beds, at the southeast 

 corner of Crosby County, Texas, with 

 a number of U. docl-umensis. Six 

 rather imperfect specimens from the Dockum beds, in the southeast 

 corner of Garza County, Texas, 1 am inclined to refer to this sjiecies, 

 though they are less elongated and nearly all of them destitute of the 

 peculiar sculpture of the type. In some of the specimens of this spe- 

 cies, the lir.T are quite distinct and regularly developed ; in others the 

 surface is nearly smooth; while others show slight, somewhat elongated 

 radiating nodules. 



UNIO DOCKUMENSIS, new species. 



Shell, oblong-oval, rounded before, somewhat pointed posteriorly; 

 umbonal region quite prominent, sculptured with distinct, radiating 

 ridges ; sides rather flattened ; ventral line straight or slightiy incurved 

 about the middle of the shell ; ventral region rather prominent poster- 

 iorly; growth lines strong; valves solid; pallial line deeply imi)ressed; 

 interior bearing a ridge running diagonally from the cardinals toward 

 the i)osterior l:)asal portion, in front of which the shell is much thicker; 

 cardinal teeth short and rather stout, laterals solid. Length, 60 mm.; 

 height, 35 mm. ; diameter, 25 mm. 



I 



