OF CONCHOLOGY. 13 '5 



? Magas patagonica, Gould, PI. 6, fig. 11, 12. 



Terehratula patagonica, Gld., Proc. Boston Soc. Nat. Hist. 



Dec. 1850. Otia Conch, p. 97. Ex. Exp. shells pi. 44, 



fig. 583, 583e. 

 Waldheimia patagonica, Gld., Otia Conch. Rect. p. 246, 



Index p. 256. 

 Terehratulina ? patagonica, Suess, Wohns. der Brach. ii, p. 16. 



Hah. Patagonia, Orange Harbor, U. S. Ex. Exp. Smith- 

 sonian Cabinet, 5965 (type). Mus. Comp. Zool. 



This species (which must not be confounded with the fossil 

 Waldheimia patagonica, Sby., Darwin's S. Am. p. 252, pi. ii, 

 fig. 26, 27, 1846, and Gray, B. M. Cat. p. 60), was originally 

 referred by Dr. Gould to Terehratula, and, in his rectification, 

 to Waldheimia ; it seems to be a true 3Iagas, and among a lot 

 of small specimens referred by Mr. Reeve to Terehratella dorsata 

 (juv), I found a number of specimens, although the type was 

 supposed to be unique. In the type specimen the apophyses 

 are broken off, but the septum remains intact. 



The shell is of a waxen white color, fan-shaped, moderately 

 oval or transverse, ornamented with rounded divaricating ribs 

 or plications which are evanescent at the apices of the valves 

 and strongest at the margin. It is generally compressed, though 

 a moderate degree of inflation exists in a few individuals. The 

 neural valve is most inflated and has a prominent beak slightly 

 recurved and pointed at the apex, beneath which is a large 

 horse-shoe-shaped foramen, with parallel sides and widely sepa- 

 rated deltidia. The latter are narrow and long, divided by an 

 impressed line from the false area, which is short and very wide. 

 The hasmal valve is provided with an inconspicuous but acute 

 apex, and small, moderately wide cardinal process. The teeth 

 and sockets are moderately strong and the former are not sup- 

 ported by laminae. The punctures are very prominent, both 

 inside and outside, and almost visible to the naked eye. They 

 are quite circular. 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 sides of the sockets, ex- 

 tending obliquely inward for a short distance, and attached 

 to the cavity of the apex, forming a triangular ridge in the 

 median line, from which the septum takes its rise. The latter 

 is broad and biangulate at its neural extremity. Two liajmal 

 processes, provided with short pointed crura, proceed from the 

 sockets and are attached, about midway between the valve and 

 tiie apex of the septum, to the latter. From the posterior apical 



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