152 Studies in Geology, Xo. 3 



Chionc (Chionc) angelana n. sp. 

 Plate IX— Figs. 10, 11. 

 Chionc sp. indet. B. Nelson, Trans. Conn. Acad., vol. 2, p. 203, 1870. 



Shell large, plump, somewhat elongate. Similar to Chione 

 variabilis except for following features : Anterior dorsal 

 margin ascends sharply, making a sharp U-shaped depres- 

 sion in the outline before the beaks. Ventral margin broadly 

 elliptical. Posterior margin almost angular ; valves produced 

 both anteriorly and posteriorly. Beaks more inclined 

 forward and much more strongly prosogyrate than in 

 variabilis. Lunule deeper, more sharply set off, more per- 

 fectly heart-shaped. Length, 55 ; height, 44.5 ; diameter, 

 34 mm. 



The fornis which are grouped under the specific limita- 

 tions here outlined are sufficiently constant in their differ- 

 ences from Chione variabilis to make necessary their recog- 

 nition as a separate species. Both C. angelana and C. vari- 

 abilis are apparently fairly abundant in the Upper Zorritos 

 formation ; lumps of fossiliferous marl from several local- 

 ities show fragments of the characteristic sculpture in some 

 profusion. Xelson mentioned C. angelana as an indetermi- 

 nate species, but his specimens, poor though they are, offer 

 sufficient evidence to permit their classification and description. 

 C. angelana differs from C. imlli Guppy (loc. cit.) in being 

 larger, more produced anteriorly, flatter basally, and wdth a 

 more deeply impressed lunule. Otherwise the two are closely 

 similar. 



Upper Zorritos. Quebradas de las Alturas, de los An- 

 geles and del Toro. 



Chione (Chione) propinqna n. sp. 



Plate IX— Fig. 12. 



Shell of medium size, subtrigonal, inflated. Anterior 

 margin rounded, ventral margin arcuate. Posterior margin 



