CLASS FIRST. 



UNIVALVE TESTACEOUS MOLLUSCA. 



ORDER I CEPHALOPODA. 



Head' of the animal emanating from a bag-sliaped mantle, and 

 surrounded by inarticulated arms, provided with a sucker, and in- 

 vesting the mouth; two sessile eyes; mouth furnished with two 

 horny mandibles ; three hearts ; the sexes in separate individuals. 



Family I — Nautilacea. 



Shell discoid, with a central spire, the cells short, and not ex- 

 tending from the centre to the circumference. 



Genus 1 Nautilus. — Linnceus. 



Shell discoid, spiral, multilocular, with simple partitions ; volu- 

 tions contiguous, the last or body-one enveloping the rest ; the 

 septa transverse, and externally concave, perforated in the disc ; 

 margins entire. 



1. A T . Becarii, pi. I, f. 11. — First Edition, pi. 52, f . 1 1 ; Montagu's Testacea 

 Britannica, p. 186, pi. 18, f. 4; Walker's Minute Shells, f. 63. 



Shell with four or five volutions, the joints deeply sulcated ; ten septa in the first 

 whorl ; convex above, and flat beneath, the markings less distinct, aperture turned 

 downwards, and not clasping the body volution ; siphon small, and usually situate in 

 the convex front ; covered with a brown epidermis, but white when divested of its 

 skin ; in which condition, if the animal is alive, it is of a crimson colour, size not a 

 line. Found on the Devonshire coast, and in the Frith of Forth, adhering to the 

 Fucus vesiculous, the roots of Alga?, and on Oyster shells. 



2. N. Becarii perversus, pi. I, f. 12 First Edition, pi. 52, f. 12; Montagu, p. 



1ST, pi. 18, f. 6 ; Walker, f. 64. 



Shell with the volutions reversed, and agreeing in every respect with the descrip- 

 tion of Nautilus Becarii. It cannot be considered as a lusus, because it is nearly as 

 plentiful as Becarii. 



3. N. crassulus, pi. I, f. 5 — First Edition, pi. 51, f. 5; Montagu, p. 191, pi. 

 IS, f. 2 ; Walker, f. 70. 



Shell strong, spiral, with numerous close-set elevated septa ; sides compressed, 

 similar, doubly umbilicated ; within which, part of the interior volution is seen ; aperture 

 placed a little oblique, scarcely clasping the body, and provided with a siphon; colour 

 cream white, sometimes brownish ; size not more than half a line. Found at Ile- 

 culver ; very rare. 



4. .V. umbilicatulus, pi. I, f. 8. — First Edition, pi. 52, f. 8; Montagu, p. 191, 

 pi. 18, f. 1 ; Walker, f. 69. 



Shell spiral, compressed, umbilicated on both sides, subpellucid, with nine or ten 

 raised sept.i ; aperture clasping the body volution almost equally on both sides, the 

 interior volutions being hid. The most minute of all the Nautili, about the fourth of 

 a line in size. 



5. N. deprcssulus, pi. I, f. 3. — First Edition, pi. 52, f. 3; Montagu, p. 190, 

 pi. 18, f. 9; Walker, f. 68. 



Shell spiral, with about nine visible septa, radiating from the centre in curved 

 lines, distinguished by their opacity, but not embossed ; sides similar ; in the centre 

 is a small pellucid spot, which may be mistaken for an umbilicus ; the aperture does 

 not clasp the body so much as that of the N. calcar, from which it also differs in 

 being much more compressed, having no carina, and in the concamerations bcin" 

 more numerous, and being only about half the size. 



6. A*, inflatus, pi. I, f. 4 — First Edition, pi. 52, f. 4; Montagu, sup. p. 81, pi. 

 18, f. 3. 



Shell spiral, with three lobed volutions ; the first provided with five extremely 

 ventricose articulations ; anterior end subglobose ; siphon situated as in N. Becarii. 

 It is smaller, and less depressed than that shell, having only about half the number 

 of articulations, which are much more tumid ; colour opaque brown. Found amon<* 

 sand on the Devonshire coast; rare. 



7. N. lurkjatulus, pi. I, f. 9, 10 First Edition, pi. 52, f. 9, 10; Montagu, 



p. 188, pi. 18, f. 7, 8; Walker, f. 67. 



Shell spiral, with ten smooth, pale ferruginous brown, flexous rays marking the 

 septa, which are rather deeper in colour, a little raised and radiating from the centre; 

 both sides are equally and considerably convex, declining towards the edge, which is 

 rounded but not strictly carinated ; aperture surrounded by a rim forming a triangle, 

 so that, the body is not intersected by the anterior end, but the volution is lost just 

 below the margin of the first septum; thus differing from the N. calcar, whose 

 body is much clasped by the margin of the anterior septum. Found at Sandwich 

 and Seasalter ; rare. 



8. A", calcar, pi. I, f. 1, 2 — First Edition, pi. 52, f. 1, 2; Montagu, p. 189, 

 pi. 15, f. 4; N. rotatus, Linna?an Transactions, VIII. p. 114. 



Shell smooth, spiral, body volution with six articulations, defined by flexous elr. 

 vated stria?, radiating from tile centre, but do not quite reach the margin, which is 

 provided with a strong carina; both sides of the shell equally convex, smoot'i, and 

 more elevated in the centre ; interior volutions invisible after entering the aperture, 

 which is semi-cordate in shape, clasping the body equally on both sides, and provided 

 with a small perforation ; colour brown. Found on the Devonshire coa^t, but very 

 rare. 



9. A', crispus, pi. I, f. 6 First Edition, pi. 52, f. 6; Montagu, p. 187, pi. 18, 



f. 5 ; Walker, f. 65. 



Shell with lateral volutions, having about twenty flexous, crenulated articulations in 

 the exterior volution, defined by elevated stria? ; back carinated ; interior volutions 

 hidden ; aperture semicordate, equal, lateral, clasping the body, and provided with a 

 small siphon; glossy and pure white. Found at Sandwich, Sheppy Island, Teign- 

 mouth, and Salcomb, Devonshire ; and at Weymouth and Swanage, Dorsetshire , 

 also the south coast of Wales. 



10. N. carinatulus, pi. I, f. 7 First Edition, pi. 52, f. 1; Montagu, p. 195; 



Walker, f. 72. 



" An oblong carinated shell, with a narrow oval aperture; colour whiteish, trans- 

 parent like glass. From Seasalter and Sandwich; very rare." We have copied 

 this, imperfectly figured and described, Shell from Walker. From the figuie we 

 should say that it belonged to the family Spherulacea of Lamarck. 



Family II — Lituolacea. 



Shell somewhat spiral, the last volution continuous in a straight 



line. 



t 

 Genus 2. — Spirolina. — Lamarck. 



Shell multilocular, partly spiral, and discoid; volutions contiguous, 

 the last terminating in a straight line ; septa straight, perforated by 

 a tube. 



Subdivision I. — Convoluted. 



1 . .<-. suharcuatula, pi. I, f. 27 First Edition, pi. 52, f. 27 ; Nautilus subar- 



c;:<:i;i„s; Montagu, sup. p. 80, pi. 19, f. 1 ; Walker, f. 73. 



S! ell subarcuated, subconvoluted, the straight part containing about five cells; the 

 posterior half convoluted ; twelve visible concamerations, and very distinct ; septa 

 somewhat elevated; back carinated, and slightly indented at the division of the cells; 

 anterior septa oblique, producing at the aperture a considerable slope from the back 

 interiorly; front margin not carinated, but obtusely rounded ; siphon, placed near 

 the back. 



2. S. similitua, pi. I, f. 22 First Edition, pi. 52, f. 22 ; Nautilus similituus : 



Montagu, p. 196, pi. 19, f. 3. 



Shell elongated, subarcuated, with elevated articulations ; the septa provided with 

 small elevated tubercles, a row of larger ones in the centre of the back ; apex iacur- 

 vated ; aperture with a small produced siphon ; colour Opaque brown. Found at 

 Sandwich and Sheppy Islands ; rare. 



Subdivision II. — Shells nearly straight. 



3. S. Legumen, pi. I, f. 22, 23.— Orthocera Legumen.—Virst Edition, pi. 52, 

 f. 22, 23; Nautilus Legumen; Montagu, sup. p. 82, pi. 19, f. 6, and A. Walker, 

 f. 74. 



Shell subarcuated, smooth, glossy, pellucid, white ; slightly compressed, and a 

 little tapering; the extremities rounded and somewhat contracted; anterior end 

 surrounded by an oblique ridge, above which is an excerted siphon; with a consider- 

 able aperture near to the concave side; septa eight or nine in number, oblique, and 

 visible through the shell; cells gradually decreasing in size towards the posterior end. 

 Fig. 23 represents the aperture with the siphon. Length about an eighth of an 

 inch ; breadth about a sixth its length. Found in sand on the coasts of Kent and 

 South Devon ; very rare. 



Family III. — Orthoceeata. 

 Shell straight or nearly so, without any spiral volutions. 



Genus 3 Nodosaria. — Lamarck. 



Shell elongated, erect, or smooth, and slightly arcuated, sub- 

 conic, nodose, consisting of a series of spherical volutions ; the 

 transverse septa perforated. 



1. N. subarcuata, pi. I, f. 18 Orthocera subarcuata. — First Edition ; Nau- 

 tilus svbarcuatus ; Montagu, 198, pi. 6, f. 5. 



Shell subcylindrical, subarcuated, with three distinct globose articulations at the 

 superior end ; the remaining divisions imperfectly defined, and abruptly tapering to 



