238 MOLLUSCxV. CEPHALOPODA. Oethoceua. 



pers a little to the extremity, which is more obliquely placed than in the 

 others, and produced into a blunt knob at the upper margin. The aperture 

 is likewise a little contracted. 



b. Extinct species. 

 * Surface of the shell smooth. 



1. O. ItBvis Shell conical, partitions waved; chambers large; syphon 



small and central. The length of the specimen which I possess is upwards 

 of 3 inches. The breadth at the base is i^gths, and at the apex /gths. The 

 shell is very thin ; chambers about ^'oths of an inch in depth ; partitions 

 waved on both sides ; syphon in the middle of the shell about j'^th of an inch 

 ■wide. — O. superficie Isevi, [7re'« Rutherglen, 306, t. xvi. f. 3 — O. lasvis, Fkm. 

 Annals of Plul. v. 201, t. xxxi. f. 1.— In Carboniferous Limestone. 



2. O. pyramidalis — Shell tapering, partitions slightly waved ; chambers 

 large, syphon small and central. This is longer in proportion to its breadth 

 than the preceding ; the length of one specimen is upwards of 6 inches ; 1 inch 

 and -%ths at the larger end, and j-jths at the apex ; the last formed chambers 

 are nearly truths of an inch in depth, while the oldest, towards the point, are 

 scarcely I'gth. A fragment found contiguous measured 2 inches in diameter. 

 —Flem. An. Phil. v. p. 202, t. xxxi. f. 2 — In Carboniferous Limestone. 



3. O. cylindracea. — Nearly cylindrical, partitions slightly waved, chambers 

 numerous, pipe minute and central. In a specimen 3^th inches in length, 

 -•*-ths at the base, and /o^h of an inch at the apex, the chambers are scarcely 



'-th in depth. When the shell is removed, the chambers appear very dis- 

 tinct, with a flat surface — Flem. An. Phil. v. p. 202, t. xxxi. £ 3. — In Carbo- 

 niferous Limestone and Slate-clay of the coal-field. 



4. O. convexa Nearly cylindrical, partitions thin and concave ; syphon 



large and lateral. In a specimen 4^ inches long, the diameter at the base 

 was l^th, and at the apex i^oths. The lower chambers are about ^th of an 

 inch in depth. The syphon is about /o^^^ of an inch wide, and placed about 

 midway between the centre and margm — Flem. An. Phil. v. p. 202. t. xxxi. 

 f.4. O. circularis, Sower. Min. Conch, t. 60. f. 6. 7- ? — In Carboniferous Limestone. 



5. O. attenuata. — Tapering, partitions nearly circular; chambers large. 

 The shell of this species in one specimen is very thin, transparent, and glos- 

 sy, and in some places is minutely striated across. Another specimen i^^ths 

 long, |th at the base, and g'^th at the apex, contains fifteen chambers — In 

 Slate-clay of the coal-field. 



6. O. Breynii Conical, partitions waved on the syphon side ; the syphon 



itself is lateral, small, and cylindrical. — Martin, Pet. Derb. t. 39, f. 4. Sower. 

 Min. Conch, t. 60. f. 5. — Carboniferous Limestone. 



7. O. undulata Shell oval, thin, smooth ; partitions numerous, oblique, 



their edges rising, oval, with a wave on each side ; syphon lateral — In Carbo- 

 niferous Limestone. 



8. O. conJca.— Shell long, conical, aperture oval; chambers numerous; sy- 

 phon small, oval, nearly touching the margin.— Sower. Min. Conch, t.lx. f. 1, 



2, 3 In Lias. In the Geology of England and Wales, p. 268, this is con- 



sidered as the alveolus of a Belemnite. 



9. O. cordiformis.—'-'- Obconical ; base contracted ; sides convex ; aperture 

 round ;" septa numerous, placed directly across ; syphon not quite in the 

 centre, the tube of which is inflated into a globular fonn between each se^- 

 tnm.— Sower. Min. Conch, t. ccxlvii — In Limestone of the Old Red Sand- 

 sUme, Closebum, Dumfriesshire. 



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