Kmarginula. MOLLUSCA. FISSURELLADJE. ^66 



Dr Turton (Conch. Diet. 142. t. xxii. f. 81.) describes a shell as Patella 

 Nubecula, List. Conch, t. Dxxxix., belonging to this genus, in the following 

 terms : " Shell oblong, oval, sometimes a little contracted in the middle, 

 semitransparent, a little convex, white, with red or brownish rays, which are 

 broader or narrower, sometimes interrupted, and often not extending quite 

 to the crown, with numerous obscure longitudinal ribs, and a few irregular 

 transverse furrows, which give it a rather rugged appearance towards the 

 margin, crown not quite central, with an oblong perforation round which is 

 often a purplish ring ; inside white, glossy, with a purplish ring round the 

 perforation at the bottom ; the margin plain : length |ths of an inch ; breadth 

 and height about |ths. — These shells have been frequently brought to us, as 

 having been dredged off the Land's End, on the Cornish coast ; but it has not 

 occurred to us, as yet, to find them ourselves. 



EXTINCT SPECIES. 



1. F. graca ? — '' Ovate, oblong, convex, radiated ; radii decussated by ele= 

 vated lines, and thickened at the intersections ; perforation small, elongated ; 

 margin of the base crenulated." — Sotver. Min. t. cccclxxxiii. — In Crag, Ips- 

 wich. 



2. F. calthrata. — An elevated curved cone ; sides coarsely reticulated ; lon- 

 gitudinal ribs about six on each side, and one central, which is split more 

 than half way down from the apex ; base oval ; apex bent almost down to 

 the base— A"'oM'en Min. Conch, t. cxix. f. 1 — Oolite at Ancliffe. 



Gen. LXXXIX. EMARGINULA.— Conical, the anterior 

 margin of the aperture with a longitudinal slit ; tentacula 

 on footstalks ; foot fringed with filaments. 



364. E. Jissura. — Strongly cancellated by longitudinal and 

 transverse ribs; apex reflected. 



Patella exigua, List. Conch, t. Dxliii. f. 28 P. fissura, Linn. Syst. i. 



12C1. Penn. Brit. Zool. Iv. 144. t. xc. f. 151. Don. Brit. Shells, 

 t. iii. f 2. Mont. Test. Brit. 490 — Various parts of the coast, not 

 common. 



Length half an inch, breadth and height |ths ; subpellucid, brown when 

 alive, white or flesh-coloured when worn ; longitudinal-ribs strong ; vertex 

 more or less reflected, margin oval, crenated ; the branchial slit extending 



about one-fourth of the height of the shell ; inside glossy flesh-coloured 



Mr Bell describes a shell apparently belonging to this species, in the Zool. 

 Journ. i. 52. t. iv. f. 1., as having been found at Poole Harbour, under the 

 title E. rosea. It only diij'ers from E. Jissura in the variable chai"acters of the 

 apex being higher and more recurved, and the inside of a delicate rose- 

 colour. 



EXTIXCT SPECIES. 



1. E. crassa — Oval, obtusely conical, furrowed ; with four or live striae be- 

 tween each furrow ; fissure wide. — Sower. Min. Conch, t. xxxii., upper fi- 

 gures. — In Crag, Ipswich. 



2. E. reticulata. — Shell oval, reticulato-striated, vertex rather acute ; prin- 

 cipal radii twenty-four or more — Sower. JVIin. Conch, t. xxxiii,, lower figures. 

 — In Crag? Holywell. 



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