226 BRITISH SILURIAN BRACHIOPODA. 
OrtTHIs 1ESTUDINARIA, Dalman. Pl. XXVIII, figs. 13—24. 
OrTHIs TESTUDINARIA, Dal. Vet. Akad. Handl., p. 115, pl. ii, fig. 4, 1827. 
— —. Hisinger. Pet. Suecica, p. 71, tab. xx, fig. 11, 1837. 
— oo Sow. Silurian System, pl. xx, figs. 9, 10, 1839. 
— — Conrad. Ann. Geol. Report, p. 63, 1839, &e. 
—  striatTuLa, Conrad,in MS., &. Emmons, Geol. Report, p. 394, illust. 105, 
fig. 3, 1842. 
—  estupiInarIa, U/‘Coy. Synopsis Sil. Foss. Ireland, p. 35, 1846. 
— aa Hall. Pal. N. York, vol. i, p. 117, pl. xxxii, fig. 1, 1847. 
— — Phillips and Salter. Mem. Geol. Survey, vol. ii, p. 373, 1848. 
— —_— M‘Coy. Brit. Pal. Foss., p. 228, 1852. 
— _— Meneghini. Paléont. Sardaigne, p. 28, pl. a, fig. 6, 1857. 
—  srriatuLa, Salter. Quarterly Journal Geol. Soc., vol. xv, p. 380, pl. xiii, figs. 
14, 16, 1868. 
— — Salter. Siluria, 2nd ed., p.74, fig. 12,6, pl. v, fig. 1, 1859. 
— — Salter. Mem. Geol. Survey, vol. iii, p. 340, pl. xiii, figs. 10—14, 
1866. 
Spec. Char. Suborbicular or truncato-orbicular, usually wider than long, rounded or 
slightly emarginated in front; hinge-line straight, shorter than the width of the shell. 
Ventral valve moderately convex, sometimes slightly longitudinal, elevated along the 
middle; beak small, incurved, area narrow. Dorsal valve very slightly convex, at times 
almost flat, with a longitudinal depression along the middle; hinge-area narrow. Surface 
of both valves covered with numerous radiating thread-like ribs, which increase in number 
at various distances from the beaks by the means of bifurcation or by one or two smaller 
strie being interpolated between each pair of the larger ones; the valves are also crossed 
by concentric lines of growth. In the interior of the dorsal valve the cardinal process is 
situated between two small projecting, deviating, brachial laminze, while the quadruple 
muscular impressions are small and divided into pairs by a rather wide mesial ridge. 
In the ventral valve the muscular area is moderately developed, elongated, and forked in 
front. ‘T'wo specimens measured— 
Length 7, width 7, depth 3 lines. 
idl aleage fy AO, eS 
Oés. Although I have never had the advantage of being able to procure a Swedish 
example of Dalman’s Orthis testudinaria, | am inclined to believe (after a study of the 
Swedish author’s figure and description!) that our British specimens above described 
1 «QO, testa confertissime striata, costis sub-alternis elevatioribus: valva minori subplana semiorbiculari ; 
majori basi gibba, nate prominula nutante. Locus. Ostrogothia ad Borenshult, in calce cinerea. Longit. 
15 mm., latit. testee 15, lat. valvee minoris ad basin 12 mm., crass. 7 mm. 
“Species quasi media inter O. elegantulam et O. basalem, ad utraque distincta ambitu magis orbiculari, 
minime ad cordatum tendente, praesertim vero costarum radiantium ratione, que enim duplicis sunt generis, 
os 
ee ee 
