DE. T. DAVIDSON ON EECENT BEACHIOPODA. 99 



T. fibula hitherto discovered, whicli is said to have come from Bass's Strait, South 

 Australia. Those who differ fi-om mc in this identication will find T. fibula dcscril)cd 

 by Reeve in the following words : — 



" Shell orhicularly ovate, solid, smooth, whitish, tinged with rose ; beak large, trian- 

 gularly acuminated, erect ; foramen small, terminal, deltidium obsolete, area very large, 

 flat ; valves nearly equally convex, sides callous within ; loop doubly attached, septum 

 callously anchor-shaped." [Conch. Icon. pi. viii.] 



Uncertain Species. 



55. ? Magasella patagonica, Gould, sp. (Plate XVII. figs. 12-13 a.) 



Terebratula Patagonica, Gould, Proceed. Boston Soc. Nat. Hist. iii. p. 347, 1850, and United States 

 Exploring Expedition, Mollusca and Shells, p. 97, 1852. 



Waldheimia Patagonica, Gould, Otia Conch. (Rectifications) p. 246, Index p. 236. 

 "i Magas patagonica, Dall, Amer. Jouru. of Coach, vol. vi. p. 133, 1870. 

 Magasella Patagonica, Dall, Proc. Acad. Nat. Sci. Philadelphia, 1873, p. 189. 



Shell small, subpentagonal, slightly transverse or as wide as long, broadest near the 

 hinge-line. Dorsal valve very slightly convex, "oith a shallow depression along the middle 

 of the anterior half of the valve. Ventral valve deeper and more convex than the dorsal 

 one ; beak short, incurved, and truncated by an incomplete foramen, margined anteriorly 

 by a small jiortion of the umbo of the dorsal valve and by two small lateral deltidial 

 plates. Surface of valves smooth at the beak and umbo, the anterior and lateral two 

 thirds of the length of the valve being ornamented with about seventeen rounded 

 divaricating ribs of difierent lengths. In the interior the hinge-plate is wide and exca- 

 vated in the middle. The loop is doubly attached to the base of the hinge-plate, and to an 

 elevated mesial septum. Shell-punctures prominent and circular. Colour waxen white. 

 Length 6 lines, width 6, depth 3 lines. 



Kab. Orange Harbour, Patagonia (United States Exploring Expedition). 



Obs. This appears to be a doubtful species. Mr. Dall writes me that it may be a young 

 Terehratella dorsata, but he is not certain that it is so. The shell, he adds, is a typical 

 Magasella (which T. dorsuta is not). Mr. DaU describes the species at considerable length 

 on pp. 133, 13i of the ' American Journal of Conchology,' 1870 ; he says that the dorsal 

 valve is provided with an inconspicuous but acute apex, and small, moderately wide 

 cardinal process. " The hinge-plate is wide and excavated in the middle, or rather 

 there is no transverse lamina before the cardinal process and between the sockets. Instead, 

 two thin laminae are placed between the under side of the sockets, extending obliquely 

 inward for a short distance, and attached to the cavity of the apex, forming a triangular 

 ridge in the median hne, from which the septum takes its rise. The latter is broad 

 and biangulate at its nem-al extremity. Two haemal processes, provided witli short 

 pointed crura, proceed from the sockets and are attached, abovit midway between the 

 valve and the apex of the septum, to the latter. Erom the posterior apical angle of the 

 latter two broad, roundly-recurved processes arc extended posteriorly. The anterior 



SECOND SERIES. — ZOOLOGY, VOL. IV. 14 



