Smooth species. 



DE. T. DAVIDSON ON EECENT BRACHIOPODA. 193 



with a minute circular orifice beneath it, for the peduncle, i'rom which an impressed line or 

 furrow extends on the inside, posteriorly, for a short distance. Shell of rather solid texture, 

 impunctate ; perfoi-ated by very minute tubuli (?). Type D. striata, Schum. = Z). radiosa, G:\(i. 

 + D. Evansi, Dav. + Z). norvcgica, Sby. + X). ostreoides, Lamarck. 



Subgenus Discinisca, Dall, = DisciNA, auet. Lower valve more or less flattened, concave or com- 

 pressed. Ujiper valve more convex ; apices of both subceutral or subpostcrior. Lower valve 

 with a small septum as in Discinu, behind which is an impressed disk or area, externally 

 concave, and internally elevated. This is perforated by a longitudinal fissure, extending from a 

 short distance behind the septum nearly to the posterior margin, which is often slightly indented 

 behind it. Shell more or less horny in texture, minutely tubulous. Type Discina lamellosa, 

 Brod. Rve. Conch. Icon. pi. i. fig. 4, 1862. 



We are acquainted with only one recent species of Discina proper, namely the Discina 

 striata of Schumacher. 



Of Discinisca we have the following : — 



Discinisca Icevis, Sowerby, sp., 1818 (or 18.22). 



Discinisca tenuis, G. Sowerby, sp., 1817 (may be only a variety of the pre- 

 ceding species). 

 Discinisca lamellosa, Broderip, sp., 1833. 

 Discinisca atlantica, King, sp., 1868. 

 r Discinisca Cumingii, Broderip, sp., 1833. 

 Radiately striated. \ ? Discinisca antillarum, d'Orbigny, sp., 1853 (an uncertain species). 

 I Discinisca stella, Gonld, sp., 1860. 



106. Discina striata, Schumacher, sp. (Plate XXV. figs. 18-20.) 



Crania striata, Schumacher, Essai d'uu Nouveau Systeme des Hab. des Vers Test. pi. xx. fig. 1, 1817 

 (not of Defrance). 



Orhicula norveyica, Sowerby, Trans. Linn. Soc. vol. xiii. p. 464 (syn. excL), pi. xxvi. fig. 2 a to f, 

 1818 (not of Lamarck). 



Discina ostreoides, Lamarck, An. sans Vert. vol. vi. p. 337, 1819. 



Orhicula ostreoides, Rang, Man. des Moll. p. 263, 1829. 



Discina ostreoides, T. Brown, Conch. Textbook, ed. 3, p. 108, pi. xiv. fig. 8, 1835. 



Orhicula striata, G. B. Sowerby, Thes. Conch, vol. i. p. 366, pi. Ixxiii. fig. 8, 1846. 



Crania radiosa, Gould, Moll. U. S. Expl. Exped. p. 465, fig. 480 a-c, 1852. 



Discina striata, Davidson, Ann. & Mag. Nat. Hist. 2nd ser. vol. ix. p. 376, 1852. 



Orhicula Evansii, Davidson, vVnn. & Mag. Nat. Hist. 2nd ser. vol. ix. p. 376, 1852 ; and Proc. 

 Zool. Soc. 1852, p. 81, pi. xiv. figs. 32-34. 



Discina striata and D. Evansi, E. Suess, Ueber die Wohnsitze dcr Brachiopoden, Sitzungsb. k. 

 Akad. Wissensch. Wicn, Bd. xxxvii. pp. 225 & 226, 1859. 



Orhicula ostreoides, L. Reeve, Conch. Icon., IMonogr. of Orhiciila, no. 7 , pi. i. fig. 7 a-h, 1862. 



Discina striata, Dall, Bull. Mus. of Comp. Zool. Harvard, vol. iii. p. 39, 1871 ; and Cat. of the Recent 

 Species of the Class Braehioiroda, Proc. Acad. Nat. Sci. Philadelphia, p. 300, 1873. 



Shell elongated oval or circular, generally irregular in shape, sometimes exceedingly 

 thick. Valves convex. Upper valve conical and more or less elevated. Apex sub- 

 marginal, sometimes central. Lower valve less convex than the upper one, perforation 

 or foramen small, oblique, situated at about one third of the distance from the posterior 

 margin. Surface of valves radiately finely striated, the narrow riblets increasing in 

 number by the interpolation of shorter ones at various distances from the vertex or 



26* 



