124 MANUAL OF THE MOLLUSCGA, 
IIT. RANGE OF GENERA IN TIME. 
; SPE ars aoe 
. . ms et ay 5s] (Si $ - O ®D 
Genera, arranged in their Ag SS & 2 oo ese 
Order of Appearance. | 5 SB A 2550/8 88 
Sri © s oO 155 2 Si 
OCOZACHAIBHP HP IRAE 
Lituites, Raphistoma, Obolus ...........0068 — 
Camaroceras, Atrypa, Pterinea ............ 
Gomphoceras, Bellerophon, Pentamerus | —— — — 
Orthis, Conularia, Murchisonia............... | ——— — — 
Spirifera, Athyris, Posidonomya...... ..... | —— — — — | — — 
TSOATCE 2.0... ccceceecseescescecececcctcsecsersceses | = ———— — | — — — — — 
Conocardium, Megalodon, Chonetes ...... — 
WATAIOMOLPNAN. se eercessasseaccsasvevseeseen tease —_-—--—-— 
Orthoceras, Loxonema, Cyrtia.............. |  ———— — 
Pleurotomaria, Porcellia ............00.s0+00s 
Productus, Macrochilus, Streptorhynchus -_-—-— 
Gontatites, Pleurophorus ..........eececesees 
Edmondia, Myalina............ Fanyercieectaees de —_— 
PN CLEONINANcectaescrcsscsascoreesches+scccdesesnecsen || us a) Dalyan tee 
Terebratula, Pinna, Cyprina.......ccceee | 00 a  — — — — — | Ke 
MGLINN ch Moca ereccnt scence sacetsstacesstcnencstecsessns 
Gervillia, MyOConcha........ss.ecscsscseesseeses 
Ammonites, Naticella, Opis ........ccceeeee | 000000 
Trigonia, Isocardia, Thecidium ......... (2 | ——— — — | — — — 
Cerithium, Plicatula, Cardita ...............) %|————— = == == 
Trochotoma, Tancredia, Gryphea ......... —_—— 
Ancyloceras, Inoceramus, Unicardium ... ——_—— 
Astarte, Pholadomya, Corbis ............00. = = — — | 
Nerinea, Goniomya, Exogyra ...........000 —_——— 
Terebratella, Limopsis, Nezera, Argiope ... === | -— 
Baculites, Cinulia, Radiolites ............... —_—— 
Physa, Paludina, Unio, Cyrena 
Aporrhais, Tornatella, Pyrula ...........060 = SSS 
i Peciinenlus, Phetis; Crassatella .cc.....55 |) |  ——— 
Perenelia whan, tescacescncssecseces eterna on —|--— 
| Voluta, Conus, Mitra, Haliotis, &c.......... =| == 
JEEVES SPE REOOEADOA CEC OEDELCC EIGEN ERE CO GECEET == 
Helix, Auricula, Cyclostoma ............... Sr 
Pseudoliva, Rostellaria, Seraphs 
ETP ULA HO ULOWIUDUS weitass caiinascasiecscsclecneser aes = 
Argonauta, TYidacna ....cccccsecsees naenagnaa5e = 
The genera of the older rocks are believed to be nearly all 
extinct; for although the names of many recent forms appear 
in the catalogues of Paleozoic fossils, it must be understood 
that they are only employed in default of more exact infor- 
mation. Buccinum, Melania, and Mya haye been long since 
expunged; and Modiola, Nucula, and Natica, are only retained 
until the characters which distinguish them are better under- 
stoad. 
