100 DE. T. DAVIDSON ON EECENT BEACHIOPODA. 



apical angle of the septum is extended a sliort distance in front of tliem, and is somewhat 

 before the anterior front of the base." 



As justly observed by Mr. Dall, this species must not be confounded with the fossU 



Waldheimia patagonica, Sowerby, mentioned in Darwin's ' Geological Observations on 



South America,' p, 252, pi. ii. figs. 26 & 27, 1846. More material is needed for comparison 



before the specific value of this so-termed species can be definitely ascertained. I have 



only seen one young example of the shell sent to me by Mr. Dall. 



56. ? Magasella (? var.) l.evis, Dall. (Plate XVIII. fig. 4.) 



Magasella (? var.) Icevis, Dall, A Revision of the Tcrcbratulidse, Amer. Journ. Couch, vol. vi. p. 136, 

 1870. 



? Terebratula Malvince, d'Orbigny, Voy. Am. Merid. vol. v. p. 674. uo. 779, ix. pi. 85. figs. 27-29, 1847 

 (according to Dall) . 



" Shell perfectly smooth except for the light, but beautifully regular, rounded, con- 

 centric lines of growth. Outline nearly circular, beak somewhat produced, slightly 

 recurved, with a large incomplete horse-shoe-shaped foramen. The false area sharply 

 carinate and separated from the deltidia by a deep groove. The deltidia are short, mode- 

 rately wide and widely separated. Shell not inflated, of a horn-colour, and conspicuously 

 punctate. Margin of the valves straight, without any indentation or flexure. Teeth and 

 sockets slender and weak, the whole texture of the shell being exceedingly delicate and 

 papyraceous. 



The cardinal process is hardly perceptible. The hinge-plate is very thin, excavated, 

 and covers the posterior end of the mesial ridge which divides the cavity of the beak 

 below the hinge-plate into two parts. The crura are very short and delicate, the 

 hsemal processes at first slender, rapidly widen, throwing off a triangular lamina of sheUy 

 matter from the inner sides which reaches the septum and becomes consolidated with it 

 between the anterior and posterior edges, so that the posterior edge of the septum forms 

 a wall between the two triangular lamina3. In the last species \M. jlexuosa] the edge 

 does not project above the lozenge-shaped plate formed by the two laminae, and in 

 ? Magas patagonica there is only a rounded ridge between them. The septum is broad, 

 arising close to the hinge-plate, obliquely forward, and is truncate at its extremity, which 

 touches the opposite valve. The reflected loop is broad and quite circular. The cardinal 

 muscles are attached in the apical cavity of the neural valve. The peduncle is short and 

 stout, the other muscles are very slender. 



Length "34 in., breadth •32 in., diameter "16 in. 



" A single specimen was found adhering by its peduncle to a large specimen of 

 Waldheimia venosa from Orange Harbor, Patagonia. ? ' Les isles Malouines,' D'Orb. 

 I.e. 



" It is not unlike, in general appearance, a very minute specimen of W. [ Waldheimia'] 

 venosa, except that the foramen is much larger, incomplete and of a different shape. It 

 may be identical with D'Orbigny 's species, of which the apophyses are not figured, but differs 

 in its small size and rounded form." 



