DE. T. DAVIDSON ON EECENT BRACHIOPODA. 197 



the middle of the valve and forming an obtuse angle with the plane of the sunken 

 portion. Fissure oval-shaped, rather narrow, commencing close to the posterior margin 

 of the valve and extending a little more than half the length of the disk. In the 

 interior of the valves the muscular and other impressions are exactly similar to those 

 seen in Discinisca Jcevis and D. lamellosa. Length 13 lines, breadth 12 lines. 



Hah. Uncertain. 



Ohs. Sowerby describes this species in the following words : — " Shell smooth, thin, apex 

 of the upper valve near the posterior margin ; disk of adhesion obtusely angular, close 

 to the hinder edge; perforation linear." Sow^erby's figures 4 and 5 are somewhat 

 exceptional, the larger number of specimens given to me by Mr. Sowerby being more 

 regularly oval, and even rounded, and nearly resemble some of Liscina Icevis from 

 Concepcion, Chili. The group of specimens attached to one another figured by L. Reeve 

 on pi. i. fig. 5 of his Monogr. of Orhicula seem to me and, I believe, also to Mr. Dall 

 more referable to Discinisca IcEvis than to the variety (?) D. temds of Sowerby. 



109. Discinisca lamellosa, Broderip, sp. (Plate XXVI. figs. 1-S.) 



Orbicula lamellosa, Broderip, Trans. Zool. Soe. vol. i. p. 142, pi. xxiii. fig. 2, 1835; Owen, On the 

 Anatomy of the Brachiopoda, Trans. Zool. Soe. vol. i. p. 153, pi. xxiii. figs. 2-13, 1835 ; Anton, 

 Verzeiehniss der Conch, p. 21, 1839; G. B. Sowerby, Thes. Conch, vol. i. p. 3G5, pi. Ixxiii. fig. 1, 1846; 

 Davidson, Ann. & Mag. Nat. Hist. vol. ix. 2nd ser. p. 376, 1852, and Intr. to Br. Foss. Bracli. vol. i. p. 127, 

 figs. 47-49, 1853; A. d'Orbigny, Voyage dans I'Amerique meridionalc, vol. v. p. 077, 1817. 



Discina lamellosa, S. P. Woodward, A Manual of the Mollusca, pp. 336, 337, figs. 160-1(32, 1856; 

 H. & A. Adams, The Genera of llecent Mollusca, p. 584, pi. xiii. fig. 4, 1858 ; E. Suess, Ueber der 

 Wohusitze der Brachiopoden, Sitzungsb. k. Akad. Wissenseli. Wieu, Bd. xxxvii. p. 227, 1859. 



Orbicula lamellosa, L. Reeve, Conch. Icon., Monogr. of Orbicula, pi. i. fig. 3, 1862. 



Discinisca lamellosa, TfaW, Bull. ]Mus. Comp. Zoiil. Harvard, vol. iii. p. 41, 1871, and Proc. Acad. 

 Nat. Sci. Philadelphia, p. 202, 1873. 



Discina lamellosa, Davidson, Brit. Encycl. 9th ed. p. 188, fig. 10, 1876. 



Discina [Discinisca) lamellosa, Zittel, Handbuch der Paliiontologie, p. 667, fig. 491, 1880. 



Discina lamellosa, L. .Joubiu, Comptes Rendus, t. ci. p. 1170, 1885 ; Arch. Zool. exper. t. iv. 2° ser. 

 p. 161, pis. 13, 14, 1885. 



Shell circular or orbicular, about as broad as long, horny in substance ; valves convex, 

 somewhat depressed ; colour light chestnut-brown, disk in lower valve w'hite. Upper 

 or larger valve compressed, conical, or limpet-like, vertex submarginal or situated at 

 about one third of the length of the shell from the posterior margin, concentrically 

 lamcllose ; anterior half or two thirds of the low^er valve moderately convex ; in poste- 

 rior half there exists a sunken and perforated disk ; fissure narrow, commencing at a short 

 distance from the posterior margin, and extending to about two thirds of the length of 

 the disk of adhesion. Surface, with the exception of the disk, covered with numerous 

 squamose, slightly projecting, concentric lamina) (as in the upper valve). In the interior 

 of the larger valve rather more than one third of the posterior half of the valve is occupied 

 by an oblong space, on part of which are situated the scars left by the adductor muscle ; 

 the posterior pair are on a horizontal line at a short distance from the margins of the 

 valve, and separated by two very small scars attributed to the retractor muscles (?). The 

 anterior pair of adductor scars are obliquely placed at about the middle of the valve, and 

 are larger than the posterior ones. In the interior of the smaller valve the disk forms an 



