380 DISCOVERY REPORTS 



circular to oval, but also in the texture of the shell. Usually glassy, though at some 

 stations it varies from glassy, through "matt", to rough in surface texture. 



237. Lagena bicarinata (Terquem) var. occlusa, var.n. (Plate XI, figs. 21, 22). 

 Two stations: WS 83, 88. 



In this variety the marginal edges of the keels are more or less closed in. It bears the 

 same relationship to the type as did Sidebottom's var. occlusa to the type of L.fimbriata 

 (S. 1912, etc., LSP, 1912, p. 423, pi. XX, figs. 27, 28). 



Length, 0-20 mm.; breadth, 0-15 mm.; thickness, o-ii mm. 



238. Lagena revertens, sp.n. (Plate XI, figs. 23-28). 



Twelve stations: 48, 388; WS 71, 83, 86, 87, 88, 93, 221, 245, 248, 408. 



Test flask-shaped, compressed, furnished with a more or less extended or compressed 

 neck, terminating in a lipped extremity, which carries the fissurine aperture. From this 

 lip extend two keels, which may, in rare instances, encircle the shell (fig. 27). Usually 

 there is a solution of continuity at the aboral end of the shell, where the keels return 

 upon themselves in independent loops, which are separated by a space of varying dimen- 

 sions (fig. 28). This basal space in the periphery may be either smooth, or furnished with 

 a knob or projecting spine of varying size. The texture of the two faces of the shell 

 is very variable also, ranging from clear glassy transparency to a semi-opaque rugosity. 



Size variable, averages about 0-45 mm. long, 0-30 mm. broad, 0-24 mm. thick. 



The foregoing description is an attempt to portray one of the most frequent, yet 

 variable of the Falkland Islands Lagenae. It is very typical of many stations, notably 

 WS 83, 86, 93, 245 and 248, and at the same stations the full range of form and surface 

 texture may be found, thus showing the futility of any attempt to separate varieties by 

 these characteristics. It is not at all clear whether its affinities are with the keeled 

 L. bicarinata group, or with the looped L. auriciilata group, neither of which is strongly 

 represented in the area. 



239. Lagena bisulcata, sp.n. (Plate XI, figs. 29-32). 

 Four stations: WS 86, 90, 215, 217. 



Test nearly circular, slightly produced at the oral extremity which covers a fissurine 

 aperture; thick -walled, turgid, marginal wall thickened, rounded, and forming a solid 

 thick keel round the basal half of the shell ; the aboral half of each face of the shell is 

 separated from the peripheral edge by a broad, rounded shallow groove which extends 

 right round the basal half of the face; texture smooth and glassy, becoming opaque in 

 dead shells; dull and roughened in the grooves. 



Average length of good specimens about 0-30 mm.; breadth, the same; thickness, 

 0-20 mm. 



This is a very characteristic species, never very abundant. Best and most numerous 

 at WS 217. Its affinities are not very clear, but Brady ffgures a somewhat similar form 

 (B. 1884, FC, pi. lix, fig. 7) under the name Lagena quadricostulata , Reuss (?), which, 



