GASTEROPODA. 335 
PATELLA CITRULLUS (Gould). 
Testa depresso-conica, sub-equilateralis, translucida, extus rugoso-undu- 
lata, prope apicem lineis granuliferis radiata, pallide olivacea, intus 
nitida, plumbea ; fundo allido: apertura rotundato-ovata ; margine 
expanso, acuto. 
Patella citrullus, Goutp ; Proceed. Boston Soc. Nat. Hist., 11. 149. 
July 1846. Expedition Shells, 8. 
Anta. Tentacula short and stout; eyes on an enlargement at the 
external base; mantle of a pale green, darker at the edges, and finely 
crenulated, also irregularly marked by dark brown macule; back of 
head and neck dark-brown passing into green; tentacles the same 
colour, with black extremities. Branchie having the lamine disposed 
in the form of slight scollops of a pale straw-colour; edges brown ; 
foot flesh-coloured, with a median line of a hue inclining to red ; man- 
tle fringed with dark green. [. P.c.] 
SHELL sub-diaphanous, thin, sub-conical, moderately elevated, sum- 
mit prominent; apex anterior, acute, feebly incurved, usually some- 
what eroded ; a great number of faintly elevated lines, studded with fine 
tubercles or asperities, radiate from it, and become obsolete about half- 
way towards the margin. Strie of increment coarse and irregular, 
overlaying each other, so as to give the shell a rude, concentrically 
squamose aspect externally ; disk nearly oval, a little narrowed ante- 
riorly ; margin very thin and sharp, finely and irregularly undulated. 
External colour a dusky olive-green, with a shade of brown showing 
through it, ornamented with concentric, undulating lines of obscure 
white. Interior greenish-white, with bright iridescent reflections; a 
slight spatulaform deposit at the fundus, bluish at the edges and fore- 
part, passing into greenish towards the middle and posterior portions. 
Length an inch and four-fifths ; breadth an inch and one-fifth. 
Inhabits the Madeira Islands, Funchal. 
This shell resembles somewhat the skin of a cucumber, externally. 
