THE 



GEOLOGICAL MAGAZINE. 



NEW SERIES. DECADE IV. VOL. IV. 



No. VIL — JULY, 1897. 



OJRXG-XlSrJ^JL. .iLI^TICXiES. 



I. — On S03IE Fossil Entomostkaca feom South Amekica. 



By Professor T. Eupert Jones, F.R.S., F.G.S. 



(PLATES X AND XI.) 



PART II. 

 {Concluded from the June Number, p. 265.) 



§ VIII. (4) EsTHERiA Chilensis, Philippi. 

 ;. PLATE X, Figs. 4, 6. 



^stJieria. Chilensis, Philippi, " Tert. u. Quat. Verst. Chiles," etc., 

 m7, p. 223, pi. L, fig. 11. 



Valves subcircular, approaching subquadrate, like some small 

 Lamellibranchs. Umbo at the antero-dorsal corner, and at an 

 angle of 40° to the extreme curvature of the concentric ridgelets. 

 Hinge-line straight, behind the umbo, about half the length of the 

 longest diameter of the valve. The other edges rounded ; the 

 anterior nearly semicircular ; the ventral obliquely curving up to 

 meet the steeper and narrower posterior curve. 



Size. — Length, 6-4mm. ; breadth, 5"6 mm. 



In the dark-ooloured hard shale collected by David Forbes at 

 Arica, Southern Peru. 



This differs from the associated suborbicular JEstheria in the Arica 

 shale, both by its rounder shape and especially by the terminal 

 position of the umbo. Also by its more symmetrically regular and 

 more delicate lines of growth. 



Lebu, on the coast of Chili, is given, with doubt, as the locality of 

 Professor Philippi's ^. Chilensis, Fig. 5. 



This shape is not unusual among young forms ; for instance, 

 the young J^. Forhesii, " Monogr. Foss. JEsth.," pi. iv, fig. 9 ; 

 but the marginal contour difiers all round, and the Arica specimen 

 has more numerous ridgelets. The adult form of M Forbesii differs 

 still more distinctly. 



The figure of Estheria associated with IE. elliptica in the " Monogr. 

 Foss. Esth.," pi. iv, fig. 3, already referred to as an analogue of 

 Cyclestheria, may be again quoted, as having a form somewhat like 

 our Fig. 4, though more subquadrate and oblique. 



Although there is evidently a close alliance, as far as outward 

 form is concerned, between FJstheria Chilensis and Cyclestheria, Fig. 6, 



DECADE IV. VOL. IV. NO. VII. 19 



