142 Bulletin ,31 143 



borne. One valve is in the U. S. Nat. Museum. The type and 

 the one herewith figured are at Cornell. 



In the Jackson stage seairiformis typically is decidedly dis- 

 tinct from 7iuttali, but many are the forms of this species at 

 Montgomery, La., scarcely distinguishable from varieties of i*)?.!;- 

 acola and niittalliopsis. 



Aequorea is by far the most abundant at Claiborne. It 

 may be distantly related to the perovata stock. Percrassa, though 

 thick umbonally, probably belongs with trigoniata. 



Meretrix texaco'a Hams, PI. 44, Figs. 13-15. 



PI. 45, Figs. 1-3, 



M. texacola Har., Proc. Phila. Acad. Nat. Sci., 1895, p. 50, pi. 2, fig. 5 

 Harris's original description. — Size and general form as indicated by 

 the figures ; surface generally smooth about the umbones, but often more 

 or less corrugated concentricallj' towards the base, especially posteriorly ; 

 lunule in the larger specimens very indistinct, in the smaller forms bor- 

 dered by a well incised line. 



The surface markings somewhat resemble those of C. niittalMopsis 

 Heilp. , but the anterior and posterior are too pointed, the shell in general 

 too inflated,- and the umbonal angle too great for that species. The larger 

 specimens resemble 31. calif ornica Con. 



Occasional specimens of medium size, referable to this spe- 

 cies, seem to practically connect such nearly related forms as 

 niittalliopsis, Jiuttali, and varieties of securiformis ; hence, in a 

 sense, most of these designations might be regarded as varietal. 

 In Texas, we formerly designated the smaller, longer forms (pi. 

 45, figs. 2, 3), as var. tornadonis. Another Texan form simu- 

 lating in type of exterior marking the mortoni of Conrad is 

 shown by fig. i. It seems however to be simply a sport from 

 the texacola stock. 



Type. — Texas Museum. 



Horizon. — St. Maurice Eocene. 



Specimens figured. — PI. 44, figs. 13, 14, Tex. Mus. Fig. 12, 

 Lisbon, Ala., C. U. Pal. Mus. PI. 45, figs. 1-3, Texas State 

 Mus. 



Localities. — Texas : Rio Grande at Webb-Zapata county 

 line ; Smithville, Bastrop Co. ; 2 miles E, of Alto, Cherokee ; 



