Involute.] 



MOLLUSCA. 



61 



Genus 11. — Fissurella Bruguiere. 



Shell subconic, oblong, shield-shaped, or conically depressed, 

 concave within, destitute of spiral convolutions, with the vertex 

 perforated, and directed towards the front of the shell ; perfo- 

 ration subovate, elongated, or nearly round in some species ; 

 margin thickened around the inside, and generally crenulated ; 

 muscular impression visible near the inner edge, all round, 

 widest on the sides next the anterior end ; outer surface 

 striated, ribbed, grooved, or radiated from the vertex to the 

 margin, and generally decussated by lines of growth, or con- 

 centric ribs. 



I. Fissurella Gr^eca, pi. XII, f. 10, 11. 



Fissurella Grceca, First Ed., pi. 36, f. 10, 11 ; Fleming, p. 

 364; lb., Ency., p. 66; Brown, Popular Ency., II, p. 378, pi. 

 17, f. 96; Patella Graca, Linne, Syst., p. 1262; Brown, Ency., 

 p. 467; lb., Wernerian Mem., p. 533; Turton, Brit. Fau., p. 

 198; Martini, I, pi. 11, f. 98; Pennant, IV, p. 144, pi. 89, f. 

 1 53 ; Montagu, p. 492 ; Maton and Rackett, p. 236 ; Patella 

 reticulata, Donovan, I, pi. 21, f. 3. 



Shell oblong-oval, subdepressed, thick, of a dull brownish- 

 yellow colour, with numerous, strong, longitudinal ribs, radiating 

 from the vertex to the base, some of which are thicker than the 

 rest, and in some instances tuberculated by the crossing of the 

 finer, concentric, thread-like striae, which cover the whole sur- 

 face, the interstices presenting a punctated appearance; vertex 

 perforated with an oblong-ovate fissure ; inside smooth, white, 

 sometimes of a dull, pale brownish-purple ; margin not flat, but 

 somewhat indented, or arcuated at the side, and finely crenu- 

 lated on the extreme edge. Length three-quarters of an inch; 

 breadth about half an inch ; height a quarter. 



The above are the general dimensions of the species, but is 

 met with in deep water of a larger size, off the Devonshire 

 coast, as well as that of the Isle of Man ; in which locality 

 Professor Forbes dredged some very large specimens, mea- 

 suring upwards of an inch in length, and more than five-eighths 

 in breadth. 



It inhabits most of the British coasts, but is never plentiful ; 

 the Dorset, Kentish, Devonshire, and Northumberland coasts 

 may be noticed.; the Frith of Forth, the Frith of Clyde, and 

 Argyleshire coasts, in Scotland ; and Lough Strangford, Port- 

 marnock, and Dublin Bay, Ireland. 



Genus 12. — Sipho Brown. 



Shell ovate, subconic ; vertex reflected, and slightly spiral ; 

 with a small dorsal fissure situate near the vertex, terminating 

 internally by a rhombic, funnel-shaped syphon, or cup, in some 

 species, but devoid of it in others; base ovate; exterior surface 

 ribbed, or striated. 



Section I. — Cavity provided with a funnel, leading from 

 thejissure. 



1. Sipho Noachina, pi. XII, f. 14, 15, 16. 



Sipho striata, First Ed., pi. 36, f. 14, 15, 16; Brown, Conch. 

 Text Book, p. 100, pi. 14, f. 21 ; lb., Popular Ency., II, p. 378, 

 pi. 17, f. 113; Fissurella Noachina, Smith, Wernerian Mem., 

 VIII, p. 43 ; Sowerby ; Cemoria Flemingii, Leach. 



Shell brownish-white, very strong, ovate, subconic ; vertex 

 slightly spiral, and inclining anteriorly; with a small triangular 

 fissure behind, broad below and acute above, situate near the 

 vertex; aperture white, smooth, and slightly crenulated on the 

 margin. 



First discovered as British, by my friend Stewart Ker, Esq., 

 at Greenock, where dead shells are not uncommon. Two spe- 

 cimens were dredged alive, off Rothesay, by my friend James 

 Smith, Esq., of Jordan Hill, near Glasgow, while I accompanied 

 him on a dredging excursion, in his yacht, in 1837- 



It seems to have been very plentiful in the Clyde at one 

 period, as it occurs abundantly in a subfossil state in the ele- 

 vated marine bed of the Clyde, at Dalmuir. 



Section II. — Destitute of an internal funnel. 



2. Sipho radiata, pi. XII, f. 20. 



Sipho radiata, First Ed., pi. 36, f. 20; Fissurella apertura, 

 Fleming, p. 364; Patella apertura, Montagu, p. 491, pi. 13, f. 

 20 ; Fleming, Ency., p. 66 ; Patella Noachina, Brown, Ency. 

 Brit., p. 467 ; Maton and Rackett, p. 236 ; the young of Fis- 

 surella Grceca, Forbes, Mai. Mon., p. 34. 



" With a subconic, subpellucid, white shell, marked with 

 strong, longitudinal, tuberculated ribs, and a few circular ridges, 

 that give it a cancellated appearance ; vertex reflected, the point 

 very small, and turning downwards; not detached, but adhering 

 to the top of the shell, sometimes making one convolution ; 

 immediately above which is a rhomboid perforation. Inside 

 smooth, glossy, white ; margin oval, edge crenated by the ribs. 

 Length not quite a quarter of an inch, scarce an eighth of an 

 inch in height. In one instance this shell had a few brown 

 streaks running half way up the margin." — Montagu. 



In my Paper in the Encyclopa?dia Britannica, I considered 

 this the Patella Noachina of Chemnitz ; but on seeing the 

 original shell in the British Museum, I perceived that it was a 

 different species from Sipho Noachina. It is more elliptical 

 than the latter shell, the longitudinal ribs larger, set more apart, 

 and the concentric striae not so well marked ; but a stronger 

 character than these is the form of the foramen, which is nearly 

 lance-shaped in S. Noachina, with an internal funnel, whereas 

 it is oblong-ovate in S. radiata, and destitute of an internal 

 funnel ; with which character, a specimen found in sand at 

 Tenby, by General Bingham, expressly agreed. 



In 1819, when I made my drawing from Montagu's original 

 specimen in the British Museum, mv friend Dr. Leach con- 

 curred in opinion, that specimens with which I presented him, 

 from the Clyde, were perfectly distinct from that in the 

 Museum, as did also Mr. J. E. Gray ; and the Doctor agreed 

 in the propriety of instituting a new genus for their reception ; 

 but it appears he afterwards thought Cemoria a better name 

 than that which I had previously chosen. 



Found at Falmouth Harbour, Cornwall, and in Salcomb Bay, 

 Devonshire, by Colonel Montagu ; at Tenby, Wales, by General 

 Bingham ; and in Zetland, by Dr. Fleming ; and Professor 

 Forbes dredged it plentifully off the Manx coast, but considered 

 it the young of Fissurella Grceca, with which opinion I do not 

 agree. It is not half the size of S. Noachina. 



