264 Prof. T. Rupert Jones — Fossil Entomostraca , S. America. 



also fig. 16, JS. Mangaliensis ; and S!. minuta var. latitexta, Geol. 

 Mag. 1890, PI. XII, Fig. 8. These approach one another in outline 

 and ornament, but appreciable differences are readily discernible. 



Among recent species, Estlieria Dahalacensis, Straus-Durckheim, 

 and JE. Oihoni, Baird, are also straight-backed forms, with reticulate 

 ornaments between the ridges, but there are differences in outline 

 and surface. 



§ VII. (3) EsTHERiA Aricensis, sp. nov. 

 PLATE X, Figs. 1-3. 



This species is based on some specimens which the late David 

 Forbes, F.R.S., brought to England, in 1861, from Arica in Southern 

 Peru (now held by the Chilians), in 18° 25' S. lat., 70° 15' W. long. 

 These fossils have been placed in the British Museum (Nat. Hist. 

 Branch) since Estlieria Forbesii was described by me in 1862. They 

 are illustrated by Figs. 1-3, and are obliquely subcircular (not 

 unlike some forms of Posidonomya), with the longest diameter at 

 an angle of about 60° to the hinge-line. This latter is usually about 

 half the length of the valve, but sometimes two-thirds. The umbo 

 is in the anterior third of the cardinal margin, and rather prominent 

 above the hinge-line. 



The concentric ridges are numerous (16 or more), mostly large 

 and coarse, but somewhat obscured by pressure and the granular 

 sandy condition of the matrix. In one large hollow mould 

 (unfortunately imperfect, Fig. 3), vertical barrolets, or small 

 transverse rirlgelets, are visible in the broader interspaces. 



These specimens from Arica measure — 



Fig. 2, length 9-4 mm., height 80 mm. 



Fig. 1, length 13-63 mm., height 9-45 mm. 



Fig. 3 (imperfect), length 17-0 mm., height 15-02 mm. 



From a fractured internal cast of a valve, the thickness of the 

 closed carapace of a large individual may have been about 4 mm. 



They occur on the bed-planes of a hard, black, irregularly fissile, 

 sandy shale, which has weathered brown inwards to some distance 

 from the surface. According to David Forbes's label they came 

 from " Bed F, Morro de Arica." The hill near the town rises to 

 about 500 feet above the sea-level. He was there in 1857, and on 

 May 27, 1861. 



In the Quart. Journ. Geol. Soc, vol. xvii, 1861, pp. 35-6, he 

 described the section as exhibiting a succession of interstratified 

 shales and porphyries, to which, although regarded as Carboniferous 

 by D'Orbigny, D. Forbes hesitated to assign any definite age, for 

 ■want of evidence. 



These Estherice from Arica differ from Philippi's E. Cliilensis ^ by 

 the greater obliquity of the valves and more definite hinge-line. 

 Philippi's published sketch, op. cit., 1887, pi. l, fig. 11, gives, how- 

 ever, poor data for a decision. (See PL X, Figs. 4 and 5.) 



' 1887 ; see above, p. 262. 



