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S. S. BTTCKMAN ON AMMONITES FROM 



39. A Descriptive Catalogue of some of the Species of Ammonites 

 from the Inferior Oolite of Dorset. By S. S. Buckman, Esq. 

 (Communicated by James Buckman, Esq., E.G.S.) (Read 

 June 22, 1881.) 



Before commencing a descriptive catalogue of these Ammonites, it 

 may be as well to give some idea of the various beds from which 

 they come. This has been done before ; but, various mistakes having 

 crept in and new researches having given us fresh information, I 

 deem it worth while to reintroduce the subject. 



The beds under consideration begin with the " Sands " or " Pas- 

 sage-beds," also called Midford Sands. They are from about 100 to 

 150 feet, perhaps more, in thickness, with interpolated layers of 

 comminuted shells about a foot or so thick, occurring at intervals of 

 from 4 to 10 feet. These layers contain a large conglomeration of 

 broken shells, so that good specimens are scarce. I have obtained 

 from them a JRhynchonella which is probably R. cynocephala (Bichard.), 

 besides Barpoceras Moorei (Lycett), and several species of Trigonia 

 (clavellated and costate), Lima, Astarte, &c. ; and I am led to sup- 

 pose that these sands are probably equivalent to the lower part 

 of the Cynocephala stage of Lycett, in the Cotteswold Hills. 



Above these sands comes the stone of the Inferior Oolite. This 

 stone changes at certain levels, both in composition, colour, and hard- 

 ness. The Ammonites do not occur all in one bed, but this Inferior 

 Oolite stone can be very well divided into four zones, which are ex- 

 tremely well marked, but vary very greatly in thickness at different 

 localities ; and it is probably this variation in thickness, and some- 

 times almost complete absence of a zone, that has led to very much 

 confusion. 



At the base of the Inferior Oolite Limestone comes the zone of 

 Barpoceras Murchisonce. It rests on a bed of blue stone, which 

 probably belongs properly to the sands. 



The bed in which B. Murchisonce, occurs is mostly of a light brown 

 colour, sometimes well filled with iron grains, sometimes almost 

 altogether lacking them ; it is generally very hard. At Bradford 

 Abbas it is about 1 foot thick, but on Gorton Down from 3 to 4 

 feet. 



Above this comes the zone of Barpoceras Soiverbyi. This bed is 

 sometimes light yellow with iron grains, sometimes dark blue with 

 similar grains, the light yellow being soft and the dark blue hard. 

 Its range is about 3 feet at Bradford Abbas ; and at Halfway House, 

 &c. it is about the same thickness. 



Above this comes the zone of Stephanoceras Bumphriesianum, 

 which is almost entirely, if not quite, absent at Bradford Abbas. 

 At Oborne, however,, its thickness is about 5 feet, while at Louse- 



