708 G. SHARMAN AND E. T. NEWTON ON 



on all of them is the same, and their margins are very much thickened. The most perfect 

 specimen (fig. l) has both valves preserved, and only wants the umbones; its greatest 

 length is about 2*6 in., the height 2*2 in., and the thickness 1*6 in. Anteriorly the shell 

 is rounded, posteriorly it falls away obliquely from the hinge line, and has but a slight 

 tendency to angulation. The hinge line is comparatively short, and the umbones 

 appear to have been tolerably prominent. The whole surface of the shell is marked by 

 coarse radiating bands, crossed by lines of growth, and where the shell is denuded these 

 are very strongly marked, but where the surface is intact they are much less clearly 

 seen. The ligamental area has but few (three) impressed lines. This specimen does not 

 show the hinge or the lip, but one of the others (fig. 2) has a few of the longitudinal teeth 

 characteristic of Cuculkea, and another shows the inner lip to be coarsely crenulated. 

 This shell is much like the C. alta of Sowerby, from Tertiary beds of St Cruz, Port 

 Desire, Patagonia, described in Darwin's Geological Observations in South America. 

 (p. 252), but besides being less in height, and apparently having smaller umbones, its 

 ligamental area has fewer impressed lines. This shell also has much resemblance to the 

 C. decussata of Sowerby, from the Lower Eocene of Britain {Min. Conch., pi. 206), but 

 the Antarctic shell has a shorter hinge line, is more coarsely radiated, and shows no 

 angulation extending from the umbo to the posterior extremity. As this shell cannot 

 be referred to any known species, it is proposed to name it Cucullcsa Donaldi. 



Cytlierea antarctica, sp. no v. 



The one shell referred to this genus (fig. 3) does not show the hinge or the pallial line, 

 and consequently there are these elements of uncertainty in the reference, but the form so 

 closely resembles certain species of Cytherea that there is but little room for doubt. The 

 posterior part of the shell is wanting, but the lines of growth, which are strongly marked, 

 show that it was oval in outline, and probably measured 2 "3 in. in length, its height 

 being 1*8 in. ; and its thickness, when both valves were together, must have been about 

 0'8 in. This shell has some resemblance to C. orbicularis of Edwards, from the Lower 

 Eocene of Britain (Quart. Jour. Geol. Soc, vol. viii. p. 265, pi. 16, fig. 5, 1852), but 

 differs in its oval outline and less prominent umbones ; it approaches more nearly the 

 oval varieties of the species ; it is even nearer to C. Bellovacina of Desha yes (Descript. 

 Anim. sans Vert., vol. i. p. 474, pi. 32, figs. 15-17, 1860), from the Sables infer inn ■ ; 

 but the Antarctic shell has the umbones less prominent, and directed more forwards — 

 possibly also the anterior margin is more pointed, and the entire shell more oval. The 

 differences between this shell and the species just mentioned are certainly very small, but 

 having regard to its southern origin and to these slight differences, it would not be 

 well to refer it to either of the northern species, and it is therefore named Cytherea 

 antarctica. 



