40 



MOLLUSCA. 



Okthocera. 



Sowerby, Min. Conch. I. p. 132, pi. 60, fig. 5. Phillips, 

 Geo. of York. 11. p. 238. 



Shell cylindrical, elongated, tapering gradually ; septa 

 numerous, ovate, very oblique and slightly concave, approxi- 

 mate and shallow ; siphuncle placed in one focus between the 

 centre and the margin ; outer shell very thin and plain ; 

 section of an elongated oval form. 



Found in the Derbyshire Limestone ; Kulkeagh ; and 

 Bowes. 



9. O. coNicA. — The Conical Orthocera, pi. XXVIII. fig. 

 6,7. 



Orthocera conica. Sowerby, Min. Conch. I. p. 131, pi. GO. 

 fig. 1, 2, 3. Fleming, Brit. An. p. 238. 



Shell elongated, conical, smooth ; aperture ovate ; chambers 

 numerous, increasing in depth with the size of the shell ; 

 septa with even margins, and regularly concave surfaces, 

 and doubly distant from each other at the broad than at the 

 narrow extremity ; siphuncle small, oval, and almost close to 

 the margin. 



Fig. 7. represents the convex side of one of the septa. 



Found in the Alum Clay at Whitby, by the Dowager 

 Marchioness of Bath. 



'■■. 10. O. UNDiJLATA. — The Waved Orthocera, pi. XXVIII. 

 fig. 9. 10. 



Orthocera undulata. Sowerby, Min. Conch. I. p. 130, pi. 

 59. Fleming, Brit. An. p. 238. Phillips, Geo. of Yorl.shire, 

 II. p. 238, pi. 21, fig. 8. 



Shell oval, tapering considerably ; thin, smooth ; partitions 

 numerous, nearly parallel, only slightly oblique, and a little 

 concave ; their edges ascending, oval, with a wave on each 

 side, and all equidistant, five or six to an inch ; siphuncle 

 situate near the thicker end, at about a sixth part of the 

 diameter from the side of the shell, its size being about the 

 tenth of an inch ; section of a broad oval form as in fig. 10. 



Found in the Carboniferous Limestone at Scaleber, near 

 Settle, Yorkshire ; Castlcton, and Cumberland. 



11. O. ANNULATA. — The Ringed Orthocera, pi. XXVIII. 

 fig. 11,12. 



Orthocera annulata. Sowcrb}', Min. Conch. II. p. 77. 

 Fleming, Brit. An. p. 239. Phillips, Geo. of Y'orkshire, 

 p. 239. 



Shell tapering, subcompressed, with strong, slightly oblique, 

 equidistant annulations, and minute, transverse, undulating 

 striae ; a space equal to about four rings is plain near the 

 aperture, which is situate in the thicker end, within which 

 the siphuncle is placed, a little way from the side of the 

 shell ; section a little oval, (fig. 12.) 



Found in the Carboniferous Limestone of Colebrookdale, 

 Shropshire ; Bowes ; Kulkeagh ; High-Green- Wood, and 

 Northumberland. 



12. O. LATERALE.— The Lateral Orthocera, pi. XXVIII. 

 fig. 14. 



Orthocera lalerale. Phillips, Geo. of Yorkshire, pi. 21. 

 fig. 8. 



Shell tapering, smooth, slightly compressed, with equi- 

 distant, wide-set, somewhat oblique septa, their sides slightly 

 arcuated ; section a little ovate. 



Found at BoUand, Queen's County. 



13. O. Steinhaueri. — Steinhauer's Orthocera, pi. 

 XXVIII. fig. 15. 



Orthocera Steinhaueri. Sowerby, Min. Conch. I. p. 132, 



pi. 60. fig. 4. Fleming, Brit. An. p. 239. Phillips, Geo. of 

 Yorkshire, II. p. 238, pi. 21, fig. 5. 



Shell circular, very concave, with thin margins, even 

 edged, wide, elongated, tapering very gradually ; with very 

 parallel andregular transverse strJBe ; septa distant ; chambers 

 very deep ; siphuncle rather large, situate close to one side ; 

 section circular. 



Discovered, by the Rev. H. Steinhauer, in Limestone on 

 the Broadford Road, and has been met with at Bolland, and 

 in Coal Shale at Halifax. 



14. O. STRIATA. — The Striated Orthocera, pi. XXVIII. 

 fig. 17. 



Orthocera striata, Sowerby, Min. Conch. I. p. 129, pi. 58. 

 Fleming, Brit. An. p. 239. lb. VVernerian Mtm. III. p. 96. 



Shell nearly cylindrical, and tapering very gradually ; the 

 whole surfiice longitudinally striated ; aperture oval, about a 

 third broader than wide ; septa very thin, numerous, but 

 widely set; chambers deep; siphuncle large and nearly 

 central ; greatest known length eleven inches. 



Discovered in the Black Rock Transition Limestone, near 

 Cork, and in the Clay Slate of the same formation, at the 

 Cove of Cork. 



SECTION II SHELLS ARCUATED. 



— The Pear-shaped Orthocera, pi. 

 Phillips, Geo. of Yorkshire, II, 



- 15. O. PVRiroRMis 

 XXVII. fig. 1, 2. 



Orthoceras pyriforme. 

 p. 238. pi. 21, fig. 14, 15. 



Shell pyriforni, tumid towards the aperture, and arched 

 towards the smaller end ; smooth ; section oval, siphuncle 

 situate at one-third of the diameter from the edge. 



Professor Phillips sajs, " In the specimen figured the 

 large projecting plate, with its plane parallel to the axis, (as 

 in our fig. 2. pi. XXVII.) and to the longer diameter of the 

 shell, is covered on the convex side by a white, laminated, 

 friable inner shell, very analogous to the " bone" of Sepia 

 Officinalis, and to the lower laminiE of Beleranites qtiadratus. 



Found at Bolland and Kildare, Ireland. 



16. O. FUsiFORMis. — The Spindle-Shaped Orthocera, pt. 



xxvin. fig. 1. 



Orthocera fusiformis. Sowerby, Min. Conch. VI. p. 167, 

 pi. 588, fig. 1, 2. 



' Shell arcuated, fusiform, smooth, round, and tapering 

 rapidly towards the smaller end, and slightly towards the 

 broader one ; siphuncle almost central ; outer chamber large. 



Found in the Limestone at Bolland, Queen's County, 

 Ireland, and in similar Limestone near Preston, Lancashire. 



This shell is somewhat allied to the preceding. 



1 7- O. PARADOxiCA. — The Paradoxical Orthocera, pi. 

 XXVII. fig. 4. 



Orthocera puradoxicu, Sowerby, Min Conch. V. p. 81, 

 pi. 457. 



Shell lanceolate, triangular, flattened in front, with the edges 

 projecting a little, and producing a gentle concavity ; sides 

 convex, and somewhat dissimilar ; aperture forming an almost 

 equilateral triangle, with sides somewhat rounded, and slightly 

 hollowed in front ; the siphuncle almost central, but placed a 

 little nearer the front. 



Found in the Mountain Limestone of Ireland. 



18. O. Gesneri Gesner's Orthocera, pi. XXVIL fig. 9. 



