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BRITISH PALEOZOIC PHYLLOCARIDA. 



4. Aptychopsis lata, sp. nov. Plate XV, fig. 6. 



One left valve belonging to a subcircular carapace, which, when perfect, was 

 much broader across its anterior third than in its posterior region. The latter 

 is narrowed suddenly, giving a sub-cordiform outline to the perfect shield. 

 Measurements: | , 15 mm.; — , 11*5 mm.; A, 9 mm. at 60°; k _, 9 mm.; 

 I, 8 (?) mm. ; V , 60°. The frontal piece would have been more than half the 

 length of the dorsal suture ; and the whole shield probably 23 mm. long by 

 23 mm. where widest. The two valves would be broadly sagittate, or acute 

 cordiform, with re-entrant angle above ; the carapace, sub-cordiform, or broad and 

 acute obovate. Proportion : anterior width equal to length. 



This is like A. Barrandeana and A. cordiformis in the narrowing of the posterior 

 region ; but it is much shorter and relatively broader than fig. 1, and longer than 

 fig. 2 ; it has a deeper notch than figs. 1 and 14, and a larger notch than fig. 2, 

 indicating a relatively larger rostral piece. It is not sufficiently circular to match 

 either glabra or Wilsoni. 



In buffish, hard, micaceous shale ; the valve has left a rusty impression, with 

 a strong outer rim partially preserved. From a stream east of Nether Stennies 

 "Water, six and a half miles north-north-west of Langholm, Dumfriesshire. Mus. 

 Geol. Survey Scotland. M 457 c. 



5. Aptychopsis glabra, H. Woodward, 1872. Plate XV, fig. 11. 



Aptychopsis glabra, H. Woodward. Geol. Mag., 1872, p. 565. 



— — — Keport Brit. Assoc. for 1872 (1873), p. 323. 



— — — Catal. Brit. Foss. Crust., 1877, p. 69. 



— — T.R. J. and R. W. Geol. Mag., 1884, p. 354. 



— — — Eeport Brit. Assoc. for 1884 (1885), 



p. 91. 



— — Etheridge. Brit. Foss., vol. i, Palaeoz., 1888, p. 41. 



This unique test, originally circular, has been obliquely flattened, but still 

 retains the appearance of having been " finely striated concentrically." 



There are two Bohemian specimens in the British Museum (I, 2588) labelled 

 " Aptychus ? secundus" by M. Barrande, which are near allies to this form ; 

 as also are figs. 1—9, 13—15, 18, in pi. xxxiii of the ' Sil. Syst. Boheme,' vol. i, 

 Suppl. The two small and round individuals thus labelled (15 mm. in each 

 diameter, nuchal suture with slope of 40°), in shaley mudstone from Borek, may 

 be regarded, as stated above (p. 101), as Aptychopsis prima, var. secunda 

 (Barrande). 



The specimen shown by PI. XV, fig. 11, is that described in 1872. It has been 



