TRANSACTIONS OF THE SECTIONS. 91 



2. Zone of Posidonia Uronnii. — This the author divides into several. 

 n. Zone o£ Am. hi/runs. — Containing bauds of cement stone. 



;3. Zone of A7n. communis. — Constituting; the filam-shale, and characterized 

 throughout by Leda ovum. 



y. Zone of Posidonia Bronnii proper, vs^hich includes the jet-bearing beds. 

 These form the Upper Lias. 



3. Zone of Am. spinatus. — This consists of numerous ironstone bands, which 

 form the workable beds of Yorkshire. 



4. Zone of Am. niarf/aritcdu.s. — More micaceous bed.s. 



These two zones are not clearly separable, both Ammonites being found in 

 each. 



5. Zone of A7n. Davm. — This Ammonite is very rare, if found at all, in Yorkshire, 

 and the zone is more characterized by Am. capricornus. 



6. Zone of Am. Ihe.v. — This form is now recognized for the first time in Y^orkshire, 

 but the associated Ammonites, Henleiji anijindjriatus, form a well-marked zone. 



7. Zone of Atn. Jamesoni. — The true form only found «« situ north of Whitby ; but 

 the allied brevispina is highly characteristic of the beds, which are very fossiliferous. 



8. Zone of ^?«. arnudus. — This is well represented; the P/M»«ybfe;/j is conter- 

 minous with the two last zones, which end the Middle Lias. 



The last four zones are similar in lithological character, being shaly beds with 

 scattered dogger bands. 



The zones below this are only seen at Robin Hood's Bay and Redcar. 



9. Zone of Am. raricostcdns. — This is well developed in micaceous shaly beds, 

 indurated at the top, which is the character also of all the succeeding zones. 



10. Zone of Am. oxynotus. — Also well developed, containing a strong limestone 

 band. 



11. Zone of ^)H. Turneri. — Is only found on the shore. 



12. Zone of Am. vbtusus. — Seen at Peak. 



1.3. Zone of Am. Bucklandi. — Forms the lowest beds seen at Robin Hood's Bay, 

 and the highest at Redcar. They do not contain limestone as elsewhere. An 

 ichthyosanr has been found in these, such having been hitherto only announced 

 from the Upper Lias in Y'orkshire. 



14. Zone of Am. anyuJatus. — This is represented by thin shaly beds at Redcar, 

 where this Ammonite is abundant ; and also by a limestone-bed near Market 

 Weighton, at which latter place it contains a wevf and varied fauna. 



15. Zone of Am. plauorbis. — Hitherto only washed up from the sea in fragments. 

 Its beds have now been discovered near Market Weighton, where they contain 

 numerous foraminifera. In this locality the oyster-bands and white lias are reached, 

 but not the bone-bed. 



The lithological character and the position of all these zones were described 

 in the paper. 



List of Ammonites in the Author's Cabinet from the several Zones. 



Those marked P have not been found in situ, but their belonging to the zone is 

 almost certain ; those marked p probably belong to the zone. 



Zone of Aynmonitcs Jwe7isis. Ammonites crassus ( Y. &; B.) = Raquiuia- 

 Ammonites Aalensis {Zict.). nus (Z>' Orb.). 



striatulus {Sow.). Lythensis (F. S(B.). 



compactilis {Simp.). Mulgravius {Y. ^ B.). 



■ ■ leOtllS {Simp.). ry J. ^ .J 



P Jm-enais{zfef.). = gubevnv.ior{Bcan). ^"""^ oi Ammonites commimis. 



P variabilis (Z)'Ori.) = Beanii {Simp.) Ammonites commums {Sow.). 



= obliquatus {Simp.). delicatus (Si7np.). 



p fabalis (5'»«7J.) = Escheri {Haucr) ? " Bramiianus {!>' Orb.). 



Mulgravius (F. &c -S.). 



Zone of Ammonites bifrons. 



Amroonites bifrons {Bruff.) = Walcotfii ^'"o™ o^e o^' o^^^r of the above zones. 



{Sow.). Ammonites Eseri {Oppiel). 



— — - Levisoni (SMre/j.) = Samanni {0pp.). Desplacoi (B'Oi-b.'^. 



heterophyllus {Y.fB.). fibiilatus ( Y. Sf B. ). 



