FOSSIL FAUNA. 137 



PLATE LIX. 



Fossil Cephalopoda, &c. 



Fig. 1. A fossil shell named Hippurite {Hippurites bioculatus, of D"Orbigny), from the south 

 of France. This shell belongs to a family termed Rudistes, whose characters 

 are somewhat problematical, — some naturalists referring them to the bivalves, 

 and others to the univalves. The Hippurite is generally of an elongated conical 

 form, and has internally two obtuse longitudinal ridges ; the base is sometimes 

 partitioned by transverse septa. 



Fig. 5, is a longitudinal section of a specimen in which septa are displayed. The aperture 

 is closed by a moveable operculum, or upper valve, as in the specimen fig. 1. The 

 substance of the shell is cellular and very thick, and when fractured, resembles 

 that of the lamelliferous corals. Some kinds attain a large size, and are called 

 " petrified horns " by the inhabitants of the districts in the Pyrenees where they 

 abound. Though Hippurites are abundant in the chalk of the south of France, and 

 in Spain and Portugal, none have been found in England. The SpheruUte, a 

 nearly allied genus, which has no internal longitudinal ridges, occurs in the chalk 

 of Sussex : it was first discovered near Lewes. {Spherulites Mortoni, of Mantell.) ' 



Fig. 2. The siphuncle of a very large Orthoceratite (" related to the genus Ormoceras," Mr. 

 Morris), from the Rhine. 



Figs. 3 & 4, " show the direction in which the siphuncle in Orthoceratites intersects the septa." 



Fig. 6. Siphuncle of an orthoceratite (related to Orthoceras duplex, of Kissinger), from the 

 Silurian strata, Sweden. 



Fig. 7. An Orthoceratite (0. pyriforme, of Sowerby), from the Silurian strata, Dudley. 



Figs. 8 — 15. Various kinds of Belemnites. 



In the " Supplementary Notes " I have, under the head, " Belemnites,^^ explained somewhat 

 fully the nature of those fossils which, by the name of "thunderbolts," have for so many 

 centuries excited the interest and perplexed the ingenuity of collectors of fossil remains. 

 Referring the reader to that note, I shall therefore in this place merely give such specific 

 names of the specimens figured by Mr. Parkinson as I have been able to determine. 



Fig. 8. " A Belemnite of large size," Mr. Parkinson. This specimen is part of the phragmocone 

 from near the lower apical portion, partially invested with the fibrous rostrum 

 or guard. It is the species named Belemnites giganteus by M. D'Orbigny ; fi'oni 

 the Oxford clay of Wiltshire. 



' Medals of Creation, p. 428. 



