Paleontology Zorritos Formation 143 



public, as well as from similar horizons in the United 

 States. Its appearance in the north Peruvian Tertiarv offers 

 further evidence of the close relationship between the fauna 

 of those beds and the Panamanian Miocene fauna. 



The undulations on the form figured by Toula appear 

 to continue farther down on the valve than in either Brown 

 and Pilsbry's figured form or those from Peru. There is 

 thus probably some variation in this respect. The specimen 

 figured by Brown and Pilsbry shows fairly regularly spacea 

 stronger concentric threads on the ventral part of the shell; 

 in this matter, too. there is some variation, since most of 

 the Peruvian shells are evenly sculptured ventrally, and in 

 those which show heavier threads they are not regularly 

 placed. The undulatory sculpture of C. dariena is entirely 

 similar to that almost peculiar to the Inocerami, and detached 

 umbonal fragments have on that account a very misleading 

 appearance. 



dementia inoceriformis Wagner,^^^ which is found in 

 the Miocene of Maryland, is similar, but is generally more 

 delicate and less strongly sculptured. 



Lower and Upper Zorritos. South of Quebrada de las 

 Alturas. 



Subfamily ^Ieretricixae 



Genus Transennella Dall. 



Transennella heniderana n. sp. 



Plate IX— Figs, i, 2. 



Shell large and heavy for the genus, inflated. Anterior 

 dorsal margin concave; posterior dorsal margin nearly 

 straight ; ventral margin elliptical. Marginal extremities not 

 known. Umbones full, high, prosogyrate, inclined forward. 

 Surface convex excepting the lunular excavation. Sculpture 



Md. Geol. Surv., Miocene, p. 315, pi. 82, figs. i. 2, 1904. 



