RANGE OF FAMILIES IN TIME. 125 
IV. RANGE OF FAMILIES IN TIMH. 
S| 4. Asta oS oe es 
of Strata. qEeEE Ze ee ols = ss 
fe i  E | Om eID 
IORAOCHIAHPHP|R AA 
PAE MGLLEE  oelescanrsenccesescosceriarsessse i 
Teuthide—Sepiade .........:esesceeeeerees ee es Je 
REE MITNTI CCE) cc iciensevecsceceectevecseesesiooee te an Set riae 
Nuutilide...... Neer atccisntaatenaceees Se 5) ee es 
Ammonitidee es ee 
MOUEHOGELAGIOCE! | isccccsocccesccvecteccocccesee | ———— —— — pel 
Atlantide—Hyaleide ..........:eecee8888 | —— — — — | — — — — — pO Re 
Strombidee—Buccinid# ........csceeeeeee iS |) Eee eee 
MOONE —VOLULIT Gs biiccceccccseccctecesos 1 ce ll i Apes 
Naticidee—Calyptreeidze ..........cseeesee = | — SS eee ee 
Pyramidellidze ...........c:essesseeseeeerees | — —— — — — | — — — — — PR ah ge 
Reta eo GORING cs ccasccecasaeaee We) 2) 8 oS eS 
Turbinidszee—lanthinidc .........0....066. | — — — — — | — — — — — oS Ug Sees 
Fissurellide—Tornatellidé...........0056 See ee |P oS ee ee 
MEGS ALCUIG sctsessccheccsesceacsnes foie il) 0). j= SS 
Peete TEAC ER coon sccscadscleccsseserceessneee ae Ne ee ee ecie | Poe ee 
GUIGONIAE occ... cccceccoceccesecessssseeeees | — — — SS — | SS SS SS 
TET ENTS a sentation a GRE OBCB BES BSE CBE PICO REE Cer ial [leat ipa temh (camn NNN Ip emeanre reper | [ec 
Helicide—Limacid& ..........cceeeeeeees i 
Limneide—Melaniad@ .............00008 es SS | SS 
Auriculidee—Cyclostomide.............+. —|———— 
SHAE UAL IG Bier. caecccass saticosseaevessaceaes peep Nee ee pe ee ee 
Rhynchonellida@ .........cesseeessseeeeseeeees | = — — — | —— — — — | —-— — — 
Spiriferidee—Orthidee .............2.000008 | —— — — — i 
PLOGUCtIG2 ..........cccceccccceeescereesesees | —— — 
Craniadee—Lingulide ..............ce0088 | = — — — | — KH — ee a 
ALTER fice acces tec sc ve susscevsslevesinels ee eat aes 
Aviculida2—Mytilide.........cecceeeenerree | = — — — — | — — — — — | — — — — 
Arcad#@—Trigoniade ........sesesesseeees oe es || oe Seas 
PMIGIRONEIC Eee es cis selva os sls saciecice duopteccsseaes oy ee ae 
Chamide—Myade.......ccccssesccsccsernee | fe] ee 
UIP UTIL CC: <.cscccesenescvssseess podncuiadoudeio —_—— 
MM ETITIEL Smae tase vocedacsserccsecssscswaaevens —_——_— 
Cardiad2—Lucinide..........ececssecsseees 2 SS Se eee 
MMEISONOOU apes ee atch cosksecsesidcatascsen [ 2-00 8 8 te ee 
Cyprinide—Anatinide ............0.c008688 |---| KH KH eK 
PRMUEUCE Mita scesrecscctecssecetsessecceh OS a ee 
BEER —— NICO) cecevustecteetetierebe hoe fh 2 ——— | ei 
MURA GRT OS ate vs cence coves coeweseesiewsts =| SSS = 
Solenide .......... Sihivosvereiuodseesacase ees <2 — | — | — 
Gastrochenide-—Pholadide .......e | 00000 | le ee ee 
Distribution of Families of Shells in Time.—Hmploying the term 
‘families’ for natural groups of genera, and adopting the 
smallest possible number of them, we find that sixteen, or 
nearly one-fifth, range through all the geological systems. Only 
seyen haye become extinct, viz. :— 
Belemnitide. Spiriferide. Hippuritide, 
Ammonitide. Orithidee. 
Orthoceratide. Productide, 
