CEPHALOPODA. 449 



specimen of Sepia examined, the ribbon increasing in breadth backwards to 

 twice its diameter in front. 



Sciadephorus, lleinh. and Preach ; Bostrychoteuthis, Ag, = Cirro- 

 teuthis, p. 68. 



Chondrosepia (loliginiformis) Leuckart, = Sepioteuthis p. 70. 



Oioenia, Prosch, = Cranchia megalops, N. Atlantic. 



Leachia (cychira) Les. 1821; Perotis, Esch. = Loligopsis, p. 71. 



Belemnites. — Prof. Buckman of Cirencester possesses a phragmocone 

 from the lias, containing the fossil ink-bag. 



Helicerus (Fugiensis) Dana, Sill. Journ. 1848. Shell like a Belemnitc, 

 half an inch in diameter ; guard thick, subcylindrical, fibrous ; fhragmocone 

 slender, terminating in a fusiform spiral nucleus. In slate-rock, Cape Horn. 



Co;«o^(?w^/z/,s l)«jom/««z/,soccursin the (?«2«//'ofFolkstoue.(Mus. Bower bank.) 



Nautilus. — The gas with which the air-chambers of the pearly nautilus 

 are filled, consists chiefly of nitogen, without a trace of carbonic acid. {Vrolik, 

 An. Nat. Hist. ] 2, 1843.) 



Nautilus regalis. Shy, London Clay, Highgate. This species is distin- 

 guished by serrated lilies on its external surface, nearly, but not quite con- 

 cident with the lines of growth. {Wetherell, Lond. and Edin. Phil. Mag 

 IX. p. 462.) 



Orthoceras. — The species figured (PI. II. 14) is 0. Ludense, of the 

 Ludlow-rock, Herefordshire. 0. giganteum is an Actinoceras, with a large 

 beaded siphuncle, differing in structure, however, from the Silurian species ; 

 the vascular tubes (or interspaces) connecting the inner siphuncle with the 

 air-chambers exist in only one plane, on the ventral (?) side, whereas in 

 J, Bigsbyi they radiate equally in all directions. 



Hormoceras, Stokes. — The structure of the siphuncle in this fossil is 

 essentially the same as in Actinoceras ; the specimen (fig. 48, p. 88) is now 

 in the British Museum. 



DiscosoRUS (conoideus) Hall, 1852, Pal. New York, 99. This fossil 

 appears to be a siphuncle similar to those figured by Dr. Bigsby in 1824 

 (Geol. Trans. PI. 3U. f. 6.) and which have been correctly referred by 

 Quenstedt to the OrtJiocerata. It resembles a, pile of disks, and is more or 

 less curved, and conical, the smaller end being upwards or towards the last 

 chamber ! 



Conoceras (angulosus) Bronn, 1830, was founded on a fig%ire of a 

 weathered fragment of Gonioceras, as pointed out by M. Saeraann. 



Thoracoceras (vestitum) Fischer, 1844 = Melia, Fischer (not L.) 1829, 

 Carb. limestone of Moscow ; the siphuncle is small and lateral. According 

 to M. D'Orbigmy the'-, are 20 species, ranging from the L. Silurian to the 

 Carb. System, found in the U. States and Europe. 



Apioceras (trochoides) Fischer, 1844. Dev. — Carb. Europe, Brit. (e. g. 

 O.fusiforme) Aperture sub-circular, not much contracted. 



