Orthocera. 



MOLLUSCA. 



33 



12. B. CoKNU-AniETUS. — The Ram's Horn Bellerophon, 

 pi. XXVI. figs. 31, 32, 33. 



Bellerophon Cornu-Arietus. Sowerb}', Min. Conch. V. 

 p. 108, pi. 46y, figs. 2, 2. Fleming, Brit. An. p. 338. 

 Phillips, Geo. of Yorkshire, 11. p. 231, pi. 17, fig- Ifi. Nau- 

 tilus, Ure's History of Uutherglen, &c. p. 308, pi. 14, fig. 8. 



Shell very thick, smooth, and somewhat compressed ; volu- 

 tions few, the inner ones very small, rapidly enlarging and 

 much expanding towards the aperture; near which, on the back, 

 it is provided with a longitudinal, carinated, regular, dorsal 

 sinus, which divides the aperture into two lobes; aperture 

 large and greatly dilated ; axis solid and very thick. 



The inner volutions are apparent in the cast, fig. 32. 



Found in the Limestone of Kendal ; Nortliumberland ; 

 Renfrewshire, and in the Carboniferous Limestone of Lin- 

 lithgowsiiirc. 



13. B. OvATUs. — The Oval Bellerophon, pi. XXVL 

 fig. -IB. 



Ellipsolites ovatus. Sowerby, Min. Conch. L p. 83, pi. 37. 

 Nautilus ovatus. Fleming, Brit, An. p. 231. 



Ovate, gibbose, with a shallow, nearly central umbilicus ; 

 inner volutions concealed ; sides of the shell rounded ; sur- 

 face smooth ; aperture obtusely sagittate, witli its sides 

 narrow ; greatest diameter thrice the thickness of the shell. 



Found in the Limestone of Black Rock, near Cork, by 

 Samuel Wright, Esq. 



Family III.— OHTHOCERATA. 



Shell straight, or nearly so, and destitute of any spiral 

 volutions. 



Genus X.— ORTHOCERA.— Zamrtrc/l. 



Sliell elongated, subconie, straight, or slightly arcuated, 

 with numerous external, longitudinal grooves ; cells 

 formed by transverse septa, perforated by a tube, which 

 is either central or marginal. 



SECTION I. SHELLS STRAIGHT. 



1. O, coRDiFouMis. — The Heart-Shaped Orthocera, 

 pi. XXVn. fig 3. 



Orthocera cordiformis. Sowerby, Min. Conch. III. p. 85, 

 pi. 247. Fleming, Brit. An. p. 238. Ure, Hist. Ruther- 

 glen, &c. p. 306, pi. 17, fig. L 



Shell obconical, heart-shaped 

 round ; surface smooth and plain ; 

 directly across the shell ; siphuncle not quite central ; tlie 

 'tube of which is inflated into a globular form between each 

 septum, the last chamber more contracted at its opening tiian 

 at its base. 



This large species measures nine inches and a quarter in 

 length, and seven inches at the broadest part. 



Found in tiie Limestone of the Old Red Sandstone, at 

 Closcburn, Dumfries-shire by C. S. Minteith, Esq. 



2. O. ciGANTEA. — The Gigantic Orthocera, pi. XXVII. 



; sides convex ; aperture 

 septa numerous, extending 



fig. G. 



Orthocera gigantea, Sowerby, Min. Conch. III. p. 81, pi. 

 246. Fleming, Brit. An. p. 239. Phillips, Geo. of York- 

 shire, II. p. 237, pi. 21, fig. 3. 



Shell straight, gradually tapering ; finely striated ; aperture 

 oval, somewhat more than eight inches in diameter ; septa 

 direct, deep, and numerous ; siphuncle situate at a little 

 distance from the centre. 



This gigantic species is supposed to grow to the extent of 

 eight feet, and is, consequently, the largest of all the known 

 testaceoe. The shell is about a (juarter of an inch in thickness. 

 This magnificent fossil was discovered by Charles Stewart 

 Menteith, Esq. in the Limestone on his estate of Closeburn, 

 Dumfries-shire, and has since been met with at Flashy, and 

 at Bolland, Queen's County, Ireland. 



3. O. ANGULAKUs. — The Angular Orthocera, pi. XXVII. 

 fig. 5. 



Orthoccras angulare. Phillips, Geo. of Yorkshire, II. p. 

 238, pi. 21, fig. 4. 



Shell subcylindrical, with a few longitudinal furrows ; septa 

 placed very distant. 



Found at Bolland, Queen's County, and at High-Green- 

 Wood. 



4. O. iNEQUisEPTUs. — The Inequally-Partitioned Ortho- 

 cera, pi. XXVII. fig. 7. 



Orthoceras inequiseptum. Phillips, Geo. of Yorkshire, II. 

 p. 238, pi. 21. fig. 7. 



Shell straight, gradually tapering ; septa unequal, very 

 distant in the young shell ; section circular. 



Found at Bolland, Queen's County. 



5. O. RETiuuLATUs. — Tiie Reticulated Orthocera, pi. 

 XXVII. fig. 8. 



Orthoceras reticulatum, Phillips, Geo, of Yorkshire, II. 

 p. 238, pi. 21, fig. 11. 



Shell elongated ; septa distant ; surface annulated, and 

 reticulated with moniliforin lines ; sections circular. 



This figure is taken from a cast. 



Found at Bolland, Queen's Countj'. 



6. O. ciRCULARis The Circular Orthocera, pi. XXVIIL 



fig. 2, 3. 



Orthocera circularis. Sowerby, Min. Conch. I. p. 133, 

 pi. 60. fig. 6, 7. O. convexa. Fleming, An. Phil. V. p. 202, 

 pi. 31, fig. 4. lb. Brit. An. p. 238. 



Shell nearly cylindrical, or slightly tapering ; partitions 

 thin and concave, approximate, being about the sixteenth of 

 an inch distant .from each other, with their edges even ; 

 siphuncle situate about midway between the centre and the 

 margin ; diameter of the large end about an inch. 



Found in the Carboniferous Limestone at Dudley. 



7. O. ciNCTA The Girdled Orthocera, pi. XXVIII. 



fig. 4. 



Orthocera cincta. Sowerby, Min. Conch. VI. p. 168, pi. 

 588, fig. 3. Phillips, Geo. of Yorkshire, II. p. 237, pi- 21, 

 fig. 1. 



Shell elongate, almost cylindrical ; surface covered witii 

 numerous sharp, somewhat undulous, annular strias ; siphun- 

 culas central ; septa rather concave and distant ; section 

 very slightly ovate. 



Found at Preston ; Flasby ; Closeburn, Dumfries-shire, and 

 Bolland, Ireland. 



8. O. Brevnii Breyn's Orthocera, pi. XXVIII. fig. H. 



Orthocera Brcynii. Martin, Pet. Derby, pi. 39, fig. 2. 



